Biomedical subjects

I Esteban

Publications and source records attributed to I Esteban.

At least 19 recordsLinked to original sources

PubMed2004

TrkB mRNA and protein in mouse spleen: structure of the spleen of functionally deficient TrkB mice.

Whereas it is nowadays clear that neurotrophins are involved in the regulation of various aspects of the functioning of immune system, knowledge of their actual immunomodulatory roles is still fragmentary and incomplete. In this respect, knock-out mouse models remain particularly unexplored. In the present study, the expression of the TrkB neurotrophin receptor in murine spleen was addressed at the mRNA (reverse transcription/polymerase chain reaction) and protein (Western blot) levels. Once the presence of TrkB at both levels was demonstrated, the age-dependent changes in the pattern of expression of the receptor were analyzed and quantified, and TrkB-positive cells were identified by immunohistochemistry. TrkB-immunoreactive cells, identified as red pulp macrophages, were detected in the spleen throughout postnatal development and adult life; their numbers peaked at the age of 15 days. The absence of functional TrkB did not appear to result in morphological changes as assessed by light and electron microscopy of spleens from 15-day-old mice knockout for the trkB gene. The present results support the idea that, in the murine spleen, TrkB and its ligands are involved in macrophage physiology in a developmentally regulated fashion, but they do not seem to be essential for macrophage survival.

Animals↗

PubMed2003

p75NTR in the spleen: age-dependent changes, effect of NGF and 4-methylcatechol treatment, and structural changes in p75NTR-deficient mice.

In addition to their well-known actions within the nervous system, neurotrophins and their receptors are involved in immune system functioning, as demonstrated by their wide distribution in lymphoid tissues and their in vitro actions on immunocompetent cells. Nevertheless, the in vivo roles of neurotrophin-receptor systems in lymphoid tissues, as well as the scope of their influence throughout development and adulthood, are yet to be clarified. In the present study, we used combined morphological and immunohistochemical techniques to investigate the presence and cellular localization of p75NTR, the pan-neurotrophin receptor protein, in rat spleen from newborns to aging individuals, and the structural and innervation changes in the spleens of p75NTR-deficient mice. In rats, p75NTR was expressed by splenic nerve fibers and dendritic cells in an age-regulated fashion, with maximal expression detected at 2 weeks. Consistently, the spleens of newborn mice lacking this receptor protein showed no signs of ingrowing sympathetic fibers, along with an absence of defined white pulp areas. The present findings suggest a prolonged role of p75NTR in the physiology of the spleen; at least during the embryonic development period, the receptor may be critical for correct innervation and compartmentalization processes to occur.

Aging↗

PubMed2001

Reduction of glial fibrillary acidic protein-immunoreactive astrocytes in some brain areas of old hairless rhino-j mice (hr-rh-j).

Mutations in the hairless (hr) gene of mice result in hair follicle and other epithelial defects. The hr gene is expressed at high levels in the brain where it probably participates in the survival and maintenance of some neuronal populations, but whether it also supports glial populations of the central nervous system has been not investigated. To clarify this, quantitative immunohistochemistry for astrocytes (glial fibrillary acidic protein (GFAP)) and microglial cells (CD11b macrophage antigen) was used in the brain of a mutant mouse strain, the hairless (hr-rh-j) type, which carries the homozygous hr gene rhino mutation. The glial cell density was assessed in the cerebral cortex, hippocampus, striatum, hypothalamus and cerebellum of young (3 months) and old (9 months) hr-rh-j mice. No significant differences were found between young wild-type and hr-rh-j mice. The density of GFAP immunoreactive astrocytes normally increased as a function of age, but in older hr-rh-j mice there was a severe reduction (P<0.01) in the striatum, hypothalamus, and hippocampus. Conversely, the microglial cells were insensible to aging or to hr-rh-j mutation. These results suggest that the hr gene is involved in the maintenance of the GFAP immunoreactive cells in some cerebral areas. Nevertheless, because these animals do not show any neurological signs, the functional significance of the present findings remains to be established.

Aging↗

PubMed2001

Partial aortic ligature induces selective long-term c-fos like immunoreactivity in the organum vasculosum of the lamina terminalis, medial preoptic area and choroid plexus in the rat.

Partial aortic ligature causes an increase in water and sodium intake. Circumventricular brain regions are known to be involved in the regulation of these processes. In this work we use c-fos-like immunoreactivity to detect active areas involved in the long-term control of increased water and sodium intake due to partial aortic ligature. A significant increase in water intake was found on the first day after the induction, while natriophilia was observed on the fourth day. c-fos-like immunoreactivity was found selectively in the subfornical organ, the organum vasculosum of the lamina terminalis, the medial preoptic area, and the choroid plexus of the third ventricle. Present results provide further evidence for the involvement of circumventricular organs and the preoptic area in the regulation of hydromineral balance. Moreover, they suggest a maintained and long-term regulation of sodium intake by these same brain areas.

Animals↗

PubMed2001

A previous infection with Toxoplasma gondii does not protect against a challenge with Neospora caninum in pregnant sheep.

Sheep immunized with Toxoplasma gondii (Toxovax) prior to pregnancy were tested for their ability to withstand a challenge at 90 days gestation with 107 Neospora caninum (NC1) tachyzoites. The antibody responses in sheep following immunization with T. gondii were specific for T. gondii whereas peripheral blood mononuclear cells responded to both T. gondii and N. caninum antigen in vitro. This suggested that there was induction of crossreactive immune recognition in the sheep, at least at the cellular level. Following challenge of sheep at mid-gestation with N. caninum, no febrile responses were recorded in the group of sheep which had previously received Toxovax while significant febrile responses were recorded in the group of sheep which received N. caninum challenge alone. Antibody responses to N. caninum developed in all sheep following N. caninum challenge and antibody responses to T. gondii were boosted in the group of sheep which had previously been immunized with Toxovax. No antibodies to T. gondii were observed in the sheep which received the N. caninum challenge alone. Peripheral blood mononuclear cells from both groups of sheep responded to T. gondii and N. caninum antigen in vitro and interferon gamma was present in the cell-free supernatant from activated cells. However despite evidence of the induction of crossreactive immunity between T. gondii and N. caninum, this was not sufficient to prevent foetal death. The group of sheep which had received Toxovax prior to pregnancy and the group of sheep which only received the N. caninum challenge experienced 100% foetal death compared with 0% in the unchallenged control group. Vaccination prior to pregnancy with Toxovax did protect against foetal death following oral challenge at 90 days with 2000 T. gondii oocysts which caused 100% foetal death in a control challenge group.

Animals↗

PubMed2000

TrkA is necessary for the normal development of the murine thymus.

Nerve growth factor (NGF) and its signal-transducing receptor TrkA are expressed in the thymus. However, their possible role during thymic organogenesis is unknown. Here we analyze the thymus of trkA-kinase deficient 2-week-old mice. trkA-kinase +/+ and +/- mice had a normal thymus, whereas the thymus of trkA-kinase -/- mice showed lack of delimitation between the cortex and medulla, lower thymocyte density, and the presence of epithelial cell islands and numerous cysts lined with endodermal epithelium. The present results indicate that TrkA is necessary for the normal development of the thymus, and that its absence causes an arrest in the differentiation of endodermal epithelial cells. Whether this lack of differentiation has functional implication has yet to be determined.

Animals↗

PubMed2000

Development of Meissner-like and Pacinian sensory corpuscles in the mouse demonstrated with specific markers for corpuscular constituents.

The development of Meissner-like and Pacinian corpuscles was studied in mice [from postnatal day (Pd) 0 to 42] by using immunohistochemistry for specific corpuscular constituents. The battery of antigens investigated included PGP 9.5 protein and neurofilaments, as markers for the central axon; S100 protein, vimentin, and p75(LNGFR) protein, to show Schwann-related cells; and epithelial membrane antigen to identify perineurial-related cells. In Meissner-like corpuscles immunoreactivity (IR) for neuronal markers was found by Pd7 and later. The lamellar cells of these corpuscles expressed first S100 protein IR (Pd7 to Pd42), then vimentin IR (Pd12 to Pd42), and transitory p75(LNGFR) IR (Pd7 to Pd19-20). Vimentin IR, but not epithelial membrane antigen, was detected in the capsule-like cells of the Meissner-like corpuscles. On the other hand, the density of Meissner-like corpuscles progressively increased from Pd0 to Pd19-20. Pacinian corpuscles were identified by Pd7. From this time to Pd42 the central axon showed IR for neuronal markers, and the inner core cells were immunoreactive for S100 protein. Moreover, vimentin IR was detected in the inner core cells by Pd19 and later. Unexpectedly, the central axons displayed S100 protein IR (from Pd7 to P28), while p75(LNGFR) protein IR or epithelial membrane antigen IR were never detected. Taken together, and based on the expression of the assessed antigens alone, the present results suggest that the Meissner-like and the Pacinian corpuscles in mice become mature around Pd19-Pd28 and Pd20, respectively. Furthermore, these results provide a baseline timetable for future studies in the normal or altered development of sensory corpuscles in mice since specific sensory corpuscles are functionally associated with different subtypes of sensory neurons the development of which is selectively disturbed in genetically manipulated mice.

Animals↗

PubMed2000

Changes in the expression of the nerve growth factor receptors TrkA and p75LNGR in the rat thymus with ageing and increased nerve growth factor plasma levels.

The nerve growth factor (NGF) receptors p75LNGR and TrkA are expressed by thymic epithelial cells. Presumably, the NGF-TrkA system is involved in the paracrine communication between thymic epithelial cells and thymocytes, whereas the functional role of p75LNGR is still unknown. The thymus of vertebrates undergoes age-related changes that in part depend on hormonal factors. In order to find out whether thymic epithelial cells are responsive to NGF during the whole lifespan of the rat, we studied NGF receptor expression in the thymus from birth to 2 years of age, using immunohistochemistry. Furthermore, to evaluate whether increased plasma levels of NGF affected the ageing process, either NGF or 4-methylcatechol (4MC), an inductor of NGF synthesis, was administered. Both TrkA and p75LNGR were expressed by a subpopulation of thymic epithelial cells during the whole age range studied and their expression peaked at around 3 months. TrkA was primarily found in subcortical and medullary epithelial cells, whereas p75LNGR was seen in a subpopulation of medullary cells. Cortical epithelial cells, neural crest-derived cells, other stromal cells and thymocytes were not immunoreactive for NGF receptors. Neither the administration of NGF nor the increased NGF plasma levels obtained after 4MC treatment seemed to affect the ageing of the thymus as assessed by morphological and immunohistochemical criteria, but this increase in NGF levels did produce a shift in the expression of p75LNGR from epithelial cells to ED1-positive macrophages in animals of 6 months and older. Present results indicate that the expression of p75LNGR and TrkA in the rat thymus undergoes age-dependent changes that parallel those of epithelial cells. NGF could therefore be important for thymus homeostasis, possibly acting on epithelial cells. Nevertheless, NGF did not seem to be able to prevent the involution of this organ, although it produced a switch in the expression of p75LNGR, the significance of which remains to be established.

Aging↗

PubMed2000

Neosporosis. Aspects of epidemiology and host immune response.

Neospora caninum is a recently recognized protozoan parasite which has been described as causing a neuromuscular paralysis in dogs and is emerging as a major cause of bovine infertility and abortion worldwide. The parasite is known to infect a range of warm blooded animals but the disease predominates in dogs and cattle. It is not yet known if N. caninum can infect and cause disease in people. The dog has recently been identified as the definitive host and the parasite may be transmitted through the ingestion of oocysts or congenitally from mother to fetus. N. caninum is known to infect red foxes (Vulpes vulpes) and coyotes (Canis latrans) and the role of wildlife species as reservoirs of infection requires further investigation. Little is known about the range of parasite genotypes within the environment or the variation in virulence between different strains. RAPD-PCR analysis of geographically distinct bovine and canine isolates has revealed little genetic variation. Epidemiological studies from different areas of the world have investigated the importance of N. caninum as an abortifacient agent and longitudinal studies have shown the high rate (approximately 80%) of congenital transmission within infected herds. Information on the rates of repeat abortion due to neosporosis are less well defined however current estimates put this at 5% suggesting that cattle may develop some form of protective immunity against N. caninum-induced abortion. Diagnosis of the disease is based upon detection of the parasite in the tissues, most commonly using immunohistochemistry with additional information provided by serology. However, although positive fetal serology is a strong indicator of exposure to the parasite, care should be taken in the interpretation of maternal serology. As we understand more about the epidemiology of neosporosis we are also better able to interpret the results of diagnostic tests. The mere presence of the parasite does not necessarily infer that this was the primary cause of abortion. CD4+ T-cells, interferon gamma and macrophages have all been found to significantly inhibit multiplication of N. caninum tachyzoites. The nature of a protective immune response and its modulation in the pregnant animal is discussed.

Animals↗

PubMed2000

Anticardiolipin antibodies in patients with chronic hepatitis C virus infection: characterization in relation to antiphospholipid syndrome.

The antiphospholipid syndrome (APS) is usually defined by the association of clinical manifestations that comprise venous and/or arterial thrombosis, recurrent fetal losses, and thrombocytopenia, along with the presence of anticardiolipin (aCL) antibodies and/or lupus anticoagulant. Various infectious diseases can induce aCL; however, these antibodies are not usually associated with thrombotic events, as happens with autoimmune diseases, in which these antibodies need the presence of beta(2)-glycoprotein I. Levels of immunoglobulin G (IgG) and IgM aCL antibodies were determined by enzyme-linked immunosorbent assay for 243 patients with chronic hepatitis C virus (HCV) infection and 100 healthy controls. Clinical events of APS, the level of beta(2)-glycoprotein dependence of aCL, the presence of cryoglobulins and other autoantibodies, and cross-reactivity between purified aCL and HCV were evaluated. Positive results for aCL antibodies were found more frequently (3. 3%) for the patients with HCV infection than for healthy controls (0%). All positive aCL antibodies were beta(2)-glycoprotein I independent. No significant association was found between aCL antibodies and clinical manifestations of APS, neither was one found between the presence of other autoantibodies or cryoglobulins and that of aCL. Finally, no cross-reactivity between aCL antibodies and HCV antigens was observed. As previously reported, aCL antibodies seem to be an epiphenomenon, and they do not have clinical or laboratory significance in HCV patients.

Adolescent↗

PubMed1999

Expression of the neurotrophin receptor TrkB in rat spleen macrophages.

Increasing evidence suggests that some members of the family of the neurotrophins could be involved in immune system functioning. Both neurotrophins and their tyrosine-kinase signal-transducing receptors, the so-called Trk receptors, have been detected in various lymphoid tissues in a number of species. Nevertheless, their cellular localisation remains unclear in most cases. In this study, we used immunohistochemical techniques to localise TrkB in the rat spleen (from 0 days to 2 years). Cells expressing TrkB-like immunoreactivity were found exclusively within the white pulp of the spleen, along the marginal zone-follicle border and inside the follicles and periarteriolar lymphoid sheaths. These cells probably represented macrophage subpopulations, since they expressed the ED3 rat macrophage antigen. No evidence of TrkB-like protein expression in lymphocytes or follicular dendritic cells could be found. Furthermore, the density of TrkB-immunoreactive cells was observed to increase with age. Although the role of TrkB ligands in these cells remains to be clarified, the present findings provide further evidence for the supposed role of neurotrophins in immune system homeostasis.

Aging↗

PubMed1999

Lack of crossreaction with Bet v 1 in patients sensitized to Dau c 1, a carrot allergen.

BACKGROUND: Pollen-related food allergies to fresh fruit and vegetables are a well-known clinical phenomenon. Allergens related to Bet v 1 are responsible for these cross-reactions. OBJECTIVE: To characterize the allergen recognized by four carrot-allergic patients. METHODS: Sera from four patients showing strong immediate systemic reactions after contact or ingestion of raw carrot were studied by immunoblotting. The 18-kD allergen, named Dau c 1, was isolated by ethanol precipitation and specific extraction after SDS-PAGE and its N-terminal amino acid sequence was determined. RESULTS: All the patients had significant levels of specific IgE to carrot, but no specific IgE to birch pollen was detected in any of them. IgE immunodetection with the sera only recognized a single band of around 18 kD in raw carrot and in celery (with weaker reaction). No reactive band was found with birch pollen. These results were confirmed using a polyclonal anti-carrot antiserum. The carrot IgE-binding protein had a pl of 4.2 and its N-terminal sequence was homologous to that of Bet v 1 and to allergens previously described in celery and other foods. The four patients studied were not sensitized to birch pollen and three of them tolerated fruit ingestion. CONCLUSION: The whole study indicated that a sensitization to Dau c 1 induces IgE antibodies that do not cross-react with birch pollen allergens.

Adult↗

PubMed1998

A neuronal subpopulation in the mammalian enteric nervous system expresses TrkA and TrkC neurotrophin receptor-like proteins.

Increasing evidence suggests that, in addition to peripheral sensory and sympathetic neurons, the enteric neurons are also under the control of neurotrophins. Recently, neurotrophin receptors have been detected in the developing and adult mammalian enteric nervous system (ENS). Nevertheless, it remains to be established whether neurotrophin receptors are expressed in all enteric neurons and/or in glial cells and whether expression is a common feature in the enteric nervous system of all mammals or if interspecific differences exist. Rabbit polyclonal antibodies against Trk proteins (regarded as essential constituents of the high-affinity signal-transducing neurotrophin receptors) and p75 protein (considered as a low-affinity pan-neurotrophin receptor) were used to investigate the cell localization of these proteins in the ENS of adult man, horse, cow, sheep, pig, rabbit, and rat. Moreover, the percentage of neurons displaying immunoreactivity (IR) for each neurotrophin receptor protein was determined. TrkA-like IR and TrkC-like IR were observed in a neuronal subpopulation in both the myenteric and submucous plexuses, from esophagus to rectum in humans, and in the jejunum-ileum of the other species. Many neurons, and apparently all glial cells, in the human and rat enteric nervous system also displayed p75 IR. TrkB-like IR was found restricted to the glial cells of all species studied, with the exception of humans, in whom IR was mainly in glial cells and a small percentage of enteric neurons (about 5%). These findings indicate that the ENS of adult mammals express neuronal TrkA and TrkC, glial TrkB, and neuronal-glial p75, this pattern of distribution being similar in all examined species. Thus, influence of specific neurotrophins on their cognate receptors may be considered in the physiology and/or pathology of the adult ENS.

Aged↗

PubMed1998

Western blot analysis of the IgG responses of ruminants infected with Neospora caninum and with Toxoplasma gondii.

The IgG antibody responses of sheep, goats and cattle inoculated subcutaneously with live Neospora caninum tachyzoites of the NC1 isolate were analysed by Western blotting. Antibodies were detected against a wide range of NC1 tachyzoite antigens (6.5 to 80 kDa). The dominant antibody responses were directed against proteins at 36.5-38, 45.5-48.5, 52-53.5, 58, 58.5, 59.5, 60.5, 62, 63.5, 64, 66.5, 67, 67.5, 68.5 and 69.5 kDa, with sera from all three species. These sera were also used to probe blots of Toxoplasma gondii antigen and, while a number of protein bands were recognized, there was no consistency within or between animal species. The IgG antibody responses of sheep, goats and cattle orally infected with T. gondii oocysts of the M3 isolate were analysed by the same methods. Antibodies were detected to a range of S48 toxoplasma tachyzoite antigens (11 to 83 kDa). The dominant antibody responses were directed against proteins at 11, 16-17, 21.5, 22.5-23.5, 26-28.5, 32-35, 49.5, 50.5, 53, 54.5, 60.5 and 61 kDa, with sera from all three species. These sera were also used to probe blots of N. caninum antigen; antibody responses to numerous antigens were detected but showed little consistency within or between animal species.

Animals↗

PubMed1998

Immunohistochemical localization of neurotrophins and neurotrophin receptors in human and mouse salivary glands.

This study was undertaken to analyze the occurrence of low- (p75) and high-affinity (TrkA, TrkB and TrkC) neurotrophin receptor proteins in human and mouse salivary glands using immunohistochemistry. Furthermore, the presence of neurotrophins was also investigated. The study was carried out on 14 human (4 parotid, 6 submandibular and 4 sublingual glands) and 5 mouse salivary glands, using polyclonal antibodies against Trk proteins. The intensity of immunostaining was calculated automatically and evaluated in arbitrary units of grey levels. In human tissues no immunoreactivity (IR) for the assessed antigens was observed in the serous or mucous acinar cells, although TrkA IR was found in the acini of the submandibular gland. The cells of the intercalated ducts showed p75 IR (sublingual) and TrkA IR (parotid gland). The striated and excretory ducts displayed p75 IR, TrkA IR and TrkC IR in all glands, but TrkB IR was never detected. No neurotrophins were detected. In the mouse glands the ductal cells display IR for p75 (submandibular) and Trks A and C (parotid and submandibular) but not the sublingual gland. Acinar cells of the submandibular gland also show p75 IR. The only neurotrophin found in the mouse salivary glands was NGF (submandibular gland). These results suggest that neurotrophins may be involved in controlling the physiology of epithelial salivary cells.

Animals↗

PubMed1998

Expression of the TrkB neurotrophin receptor by thymic macrophages.

Increasing evidence suggests that some members of the neurotrophic factor family of neurotrophins could be implicated in the regulation of immune responses. Neurotrophins, as well as their tyrosine kinase signal-transducing receptors (the so-called Trk neurotrophin receptors), have been detected in different lymphoid tissues, although their cellular localization is not well known. In this study we used single and double immunohistochemistry to localize TrkB in situ in the rat thymus (in animals from 0 days to 2 years of age), in cytospin preparations of rat thymic cells, and in two mouse monocyte-macrophage cell lines (RAW 264.7 and J774A.1). We found TrkB protein expression in a subpopulation of cells in the corticomedullary junction, which simultaneously expressed the rat macrophage marker ED1. The density of TrkB-expressing cells increased with age, reaching maximal values at 2 years. Conversely, no evidence of TrkB protein expression could be found in dendritic cells, epithelial cells or thymocytes. Thymic macrophages in cytospin preparations, as well as in the mouse monocyte macrophage cell lines, also expressed TrkB protein. Although the possible function of TrkB in the thymic macrophage remains to be clarified, present findings add further evidence to the proposed role of neurotrophins in the immune system.

Aging↗

PubMed1997

Neurotrophin receptor-like protein immunoreactivity in human lymph nodes.

BACKGROUND: Trk proteins are essential constituents of the high-affinity signal-transducing neurotrophin receptors. They are expressed in a variety of non-neuronal tissues, including lymphoid organs, but their cellular localization in these remains to be established, as does the exact role of neurotrophins in the immune system. In this study we used immunohistochemical methods to analyze the cellular distribution of TrkA, TrkB, TrkC, and p75 (the low-affinity pan-neurotrophin receptor) proteins in normal human lymph nodes. METHODS: Formaldehyde-fixed, paraffin-embedded human lymph nodes were processed for indirect immunoperoxidase labelling, using antibodies against each Trk protein, human p75, and a panel of antibodies against B-lymphocytes (CD20), macrophages (MAC387), dendritic cells (S-100 protein). RESULTS: Immunoreactivity (IR) for p75 was observed in follicular dendritic cells of lymphoid follicles, and possibly in B cells. TrkA-like IR was seen in dendritic cells and also in some follicular dendritic cells, and in blood vessel walls. TrKB-like IR labelled scattered cells, mostly in the T cell zones, identified as macrophages, while specific TrkC-like IR could not be observed in immunocompetent cells. In no case was Trk-like IR seen in lymphocytes. CONCLUSIONS: These results demonstrate the occurrence of Trk-like proteins in normal human lymph nodes and describe their cellular localization, favoring the notion that neurotrophins have a physiological role in the immune system, possibly acting through accessory cells and not directly on lymphocytes.

Adult↗

PubMed1997

Neurotrophin receptor-like proteins in Peyer's patches.

BACKGROUND: The neurotrophins are a family of growth factors that act on responsive cells through specific high-affinity signal-transducing receptors called Trk (A, B, and C) proteins. The neurotrophin receptor proteins are widely distributed in both nervous and nonnervous tissues, including the lymphoid organs. The expression of these receptor proteins by a cell population is an indication of responsiveness to the respective binding neurotrophin. The present study investigated the presence and cellular localization of high-affinity neurotrophin receptor proteins in equine and bovine Peyer's patches. METHODS: Peyer's patches from horse and cow intestine were fixed in Bouin's fixative, embedded in paraffin cut 10 microns thick, and studied immunohistochemically using rabbit polyclonal antibodies against specific epitopes of the intracellular domain of the Trk receptor proteins. RESULTS: Immunoreactivity (IR) for Trk-like proteins was found in specific cell populations in Peyer's patches. TrkA-IR in the horse was localized in dendritic cells of the interfollicular T-cell zones and in follicular dendritic cells of the lymphoid follicles; in the cow, TrkA-ir was present in reticulum cells. TrkB-like IR was present in cells found inside lymphoid follicles of the horse, probably reticulum cells. Furthermore, in both species, TrkB-IR was found in interstitial dendritic cells and/or macrophages of the intestinal lamina propria. No specific TrkC-like immunostaining was found in immunocompetent cells of Peyer's patches. CONCLUSIONS: Present findings demonstrate that, as in other lymphoid organs, the accessory nonlymphoid cells express immunoreactivity for high-affinity neurotrophin receptor proteins. These results seem to favor the notion that neurotrophins, especially nerve growth factor, could have a physiological role in secondary lymphoid organs, possibly acting on accessory cells and not directly on lymphocytes.

Animals↗