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Biomedical subjects

L D Pearson

Publications and source records attributed to L D Pearson.

36 records · Page 2Linked to original sources
PubMed1982

Immunologic responses of the bovine fetus to parvovirus infection.

Effects of bovine parvovirus (PBV) infection on the bovine fetal immune system were studied. Five fetuses obtained by cesarean section at 5, 10, 20, 40, and 60 days after they were inoculated and 2 control fetuses at 130 and 153 days of gestation were studied. Virus was recovered from the BPV-inoculated fetuses. between 5 and 10 days postinoculation (PI) fetal blood lymphocyte counts tripled, due primarily to an increase in E-rosetting lymphocytes. There were transient increases in fetal serum immunoglobulin (Ig) M (peaking at PI day 20), marked and gradual increase in IgG1, and minimal increase of IgG2. Serum-neutralizing antibodies were detected at PI day 10 and increased to a titer of 1:2056 by day 60. Peripheral blood lymphocytes of all fetuses responded well to the nonspecific mitogens phytohemagglutinin, concanavalin A, and pokeweed mitogen. Histopathologically, there was lymphoid hyperplasia, most evident in lymph nodes draining the site of PBV inoculation. There was no indication of lymphoid depletion or necrosis in lymph nodes, spleen, or thymus of PBV-inoculated fetuses. These data indicate that under the conditions of this study, inoculation of the isolate of PBV may stimulate an immune response in the fetus.

Animals↗
PubMed1982

Mitogen-induced blastogenesis of peripheral blood and efferent lymph lymphocytes from sheep.

Peripheral blood lymphocytes and efferent lymph lymphocytes (ELL) from 20 healthy adult sheep were studied for their blastogenic responses to the phytolectins concanavalin A, phytohemagglutinin, and pokeweed mitogen. Peripheral blood lymphocytes generally incorporated significantly (P less than 0.00001) more [3H]thymidine than did ELL. The lower response in ELL, especially in concanavalin A- and pokeweed mitogen-stimulated cultures, may be due to an insufficiency of accessory cells that may be required for optimal proliferation.

Animals↗
PubMed1977

Fetal infection with bovine leukemia virus in sheep.

Several sheep fetuses were thymectomized, and their tails were removed at 58 to 65 days of gestation for tissue culture. Bovine leukemia virus (BLV) antigens were detected in serial culture of tissues from fetuses whose dams and sires were both BLV positive. However, no BLV antigens were detected in serial cultures of tissues from fetuses whose dams were negative but whose sire was positive. Precolostral serums from 3 of 16 neonatal lambs, whose sire and dams were both BLV positive, were BLV antibody positive. Thus, BLV may be vertically transmitted from a positive dam to her lamb via the placenta and/or germinal cells but not from sire to lamb.

Animals↗
PubMed1976

Lymphopoiesis and lymphocyte recirculation in the sheep fetus.

The production and the circulation of lymphocytes has been examined in the sheep fetus where neither foreign antigen nor immunoglobulins occur. It was found that as the lymphoid organs increased in size during fetal life, the numbers and the output of lymphocytes in the thoracic duct lymph increased. The recirculating pool of lymphocytes was estimated to be 5.5 +/- 1.5 X 10(8) cells in fetal lambs 95-100 days of age, 5.7 +/- 1.2 X 10(9) cells in fetuses 130-135 days of age, and 1.2 +/0 9.3 X 10(10) cells in fetuses near to term. The rate of addition of lymphocytes to the recirculating pool was 3.2 +/- 1.9 X 10(6) cells/h in fetuses of 100 days and 3.4 +/- 0.9 X 10(7) cells/h in fetuses of 130 days of age. Lymphocytes recirculated from blood to lymph in fetuses; labeled cells injected into the blood stream reappeared in the thoracic duct lymph promptly and reached maximum levels around 12-18 h after they were injected. Labeled lymphocytes were detected subsequently in greatest numbers in the lymph nodes, particularly in the mesenteric lymph nodes and in the interfollicular areas of the Peyer's patches. Chronic drainage of thoracic duct lymph from fetuses in utero for periods of up to 36 days had no obvious effects on the growth or development of the fetus and only minimal effects on the content of lymphocytes in the various lymphoid tissues even though the number of cells in the blood and lymph were reduced to between 20-30% of normal levels. Thymectomy done in fetuses about 2 mo befor cannulation of the thoracic duct reduced the output of cells in the thoracic duct to about 25% of normal levels and caused a significant reduction in the content of lymphocytes in the various lymphoid tissues. Thymectomized fetal lambs subjected to thoracic duct drainage for periods up to 2 wk in utero had a similar complement of lymphocytes in their lymphoid tissues to intact thymectomized fetal lambs. Lymphocytes obtained from the thoracic duct lymph of lambs thymectomized 2 mo previously recirculated from blood to lymph when they were injected intravenously, although they did this at a significantly slower rate than did lymphocytes from normal lambs.

Animals↗
PubMed1976

The responses of the popliteal lymph node of the sheep to Ross River and Kunjin viruses.

The responses of popliteal lymph nodes of sheep to Ross River virus (RRV) or Kunjin virus (KV) have been studied by monitoring the cell populations, virus titre, antibody titre and plaque-forming cell (PFC) content of the efferent lymph. In a typical primary response to subcutaneous inoculation in the lower hind limb of either RRV or KV, the flow rate of lymph increased slightly. Increased cell concentrations in the lymph following inoculation caused the hourly cell outputs to rise 5.3- to 10.1-fold above pre-challenge levels. High cell outputs were sustained at greater than 3-fold above pre-challenge figures for up to 10 days. The increased number of large, blastic lymphocytes ranged from 4.0- to 14.9-fold; the increase in these cells usually followed the rise in total number of lymphocytes by 24 to 48 h and remained at greater than 3-fold higher levels for up to 12 days. Ross River virus was recovered in the efferent lymph for at least 36 h after inoculation. Sudden disappearance of the virus from the lymph was correlated with the onset of significant haemagglutination-inhibition antibody titres by 3 to 4 days after infection. In the efferent lymph, PFC were detected 5 to 7 days after primary or secondary inoculation of KV or RRV when lymphocytes were incubated with specific haemagglutinin-coated goose erythrocytes and guinea-pig complement. Antibody levels in the lymph were persistent while the occurrence of PFC was transient.

Animals↗
PubMed1976

Effect of fetal thymectomy on IgG, IgM, and IgA concentrations in sheep.

Serum concentrations of immunoglobulins (Ig) IgG, IgG, IgM, and IgA were compared for normal and thymectomized lambs. Fetal thymectomies were performed in utero from 55 to 67 days of gestation. High serum IgG, IgM, and IgA concentrations occurred in all lambs after they ingested colostrum; however, the concentration of these Ig, as measured by single radial immunodiffusion, decreased exponentially during the first 16 days after birth. The half-life values for IgG, IgM, and IgA during this period in both normal and thymectomized lambs were about 25, 6, and 2 days, respectively. Increasing amounts of IgG were not detected in the serums of either group until 1 month of age. At 64 to 128 days, significantly smaller quantities of IgG and IgG were found in thymectomized lambs, whereas concentrations of IgA and IgM were similar in both groups. The results indicate that the thymus may regulate production of IgG in sheep.

Animals↗
PubMed1975

An ether-sensitive antigen associated with bovine leukemia virus infection.

An ether-sensitive antigen (es-Ag) associated with bovine leukemia virus infection was detected by immunodiffusion tests. This antigen was sensitive to ether, sodium periodate, and trypsin treatment. Based on column chromatography, es-Ag was a larger molecule than that of ether-resistant antigen (gs-Ag). With infection, precipitating antibody against es-Ag developed earlier than the precipitating antibody against the gs-Ag.

Animals↗
PubMed1974

Effects of antithymocyte sera and antimacrophage sera on cell-mediated immune reactions in Listeria-infected mice.

The cell-mediated immune responses of allograft rejection, delayed hypersensitivity, and resistance to Listeria monocytogenes were suppressed by injections of antithymocyte serum (ATS), but the immune responses were not significantly altered by antimacrophage serum (AMS) or normal rabbit serum (NRS). Antisera were prepared in rabbits against purified mouse thymocytes and purified peritoneal macrophages. When mice were injected with ATS near the time of skin grafting, allografts survived significantly longer. Similar administration of AMS or NRS failed to alter the course of graft rejection. Decreased footpad swelling indicated the suppression of delayed hypersensitivity in mice injected with ATS 6 days after a sublethal inoculation of Listeria cells. None of the serum treatments affected the ultimate survival of mice infected with a small number of bacteria. Either ATS or NRS was injected into immunized mice 1 day before and 2 days after a challenge inoculation of Listeria cells. Pronounced suppression of delayed hypersensitivity was found in the ATS-treated groups, along with extensive mortalities that reached 100% in the group receiving the largest dose of ATS. All control animals survived and demonstrated strong delayed hypersensitivity reactions. Antimacrophage serum had no significant effect on the three mechanisms of cell-mediated immunity that were tested. The lymphoid cells which mediate delayed hypersensitivity, antimicrobial cellular immunity, and allograft rejection possess antigenic determinants in common with thymocytes.

Animals↗
PubMed1974

Relationship of antimicrobial cellular immunity to delayed hypersensitivity in Listeriosis.

The relationship of antimicrobial cellular immunity to delayed hypersensitivity (DH) was studied in mice antigenically stimulated by living Listeria monocytogenes confined to diffusion chambers in peritoneal cavities or by subcutaneous inoculation of sublethal doses of the organism. Mice showed DH reactions when tested 6 days after inoculation, and reactions were positive for at least 90 days in some mice. DH also became established when the mice were stimulated by antigens diffusing from peritoneal chambers containing viable Listeria. Mice were categorized as DH positive or DH negative if they developed more or less than a 5% increase in foot volume 24 h after the injection of Listeria antigen. Some antigenically stimulated mice did not elicit the DH reaction. Consequently, the animals were arranged as immunized groups (DH positive and DH negative) and Listeria chamber implant groups (DH positive and DH negative). When challenged with L. monocytogenes, all four groups were significantly resistant as compared with controls. Thus, the in vivo tests for immunity and DH did not show direct correlation. The results suggested that antimicrobial cellular immunity can occur as a phenomenon independent of DH. Evidence for antimicrobial cellular immunity as the principle mechanism of resistance in murine listeriosis is discussed with consideration for possible heterogeneity of function by thymus-derived lymphocytes.

Animals↗
PubMed1973

Effects of antithymocyte and antimacrophage sera on the survival of mice infected with Listeria monocytogenes.

Antisera prepared in rabbits against purified mouse thymocytes (antithymocyte serum; ATS) and peritoneal macrophages (antimacrophage serum; AMS) were injected intraperitoneally into Balb/c mice infected with the bacterium Listeria monocytogenes. When administered near the initiation of infection, the ATS significantly decreased the survival time of the animals and increased the mortality rate. When ATS was administered 6 days after a sublethal dose of L. monocytogenes had been inoculated, an overt disease did not evolve. ATS that significantly potentiated primary listeriosis also had high cytotoxicity titers for thymocytes and lymphoid cells from the peritoneal cavity. Although cytotoxic activity against peritoneal macrophages could be demonstrated in lower dilutions of the ATS, this activity did not appear to correlate with the effects of the sera on listeriosis. The injection of AMS did not enhance the infectious process. In some trials more deaths occurred among mice receiving normal rabbit serum than those receiving AMS. All of the AMS had cytotoxic titers against peritoneal macrophages, and the sera were usually inactive against thymocytes and peritoneal lymphoid cells. Listeria was isolated from fatally infected mice with nearly equal success in all of the serum-treated groups, and the serum treatments did not appear to alter the pattern of gross lesions. The afferent limb of the immune response was markedly affected by the presence of antibodies to lymphocytes. However, antibodies reacting with macrophages did not demonstrably enhance the Listeria process, which depends upon cellular immunity as the principal means of acquired host defense.

Animals↗
PubMed1970

Cellular Responses of Mice to Diffusion Chambers I. Reactions to Intraperitoneal Diffusion Chambers Containing Listeria monocytogenes and to Bacteria-Free Chambers.

Diffusion chambers made with membranes having a pore size of 0.22 mum were implanted in the peritoneal cavities of mice. Chambers that contained no cells induced splenic lymphoreticular hyperplasia and a proliferation of fibroblasts around the chambers. When the chambers contained the bacterium, Listeria monocytogenes, there was strong and continuous chemotaxis of phagocytic cells to the membrane surface. The tendency to incite fibrosis around the chambers containing bacteria produced a tissue reaction resembling a chronic abscess or granuloma. The important difference from a natural lesion was the prevention of direct parasite-host cell interactions. In studies on the pathogenesis of long persisting host-parasite relationships, one might successfully use diffusion chambers to investigate the role of humoral antimicrobial substances as well as the effects of chronic inflammation, with its local concentration of metabolic products and constituents of phagocytic cells. On the other hand, the presence of diffusion chambers in the tissues is an abnormal situation and changes arising from their presence may complicate the interpretations of some experiments.

Journal Article↗