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R el Ridi

Publications and source records attributed to R el Ridi.

18 recordsLinked to original sources
PubMed1992

Age-associated decrease in proportion and antigen expression of CD8+/CD4+ thymocytes in BALB/c mice.

We studied the distribution of Thy-1.2+, CD8+ and CD4+ thymocytes in 3-, 6.5-, 12- and 18-month-old inbred BALB/c mice by staining cells with specific monoclonal antibodies (mAb) using indirect membrane immunofluorescence. The percentages of Thy-1.2+, CD8+, and CD4+ thymocytes did not vary with age until 12 months, but they exhibited at 18 months a highly significant decline. Staining thymocytes with mAb CD8 and CD4 alone or in a mixture allowed us to show that the age-related decline in proportions of CD8+ and CD4+ thymic cells is associated with the double positive (CD8+/CD4+, immature) subset. Most importantly, we observed a progressive age-related decrease in ratio of bright/dull Thy-1.2+, CD8+ and CD4+ thymocytes. The CD8+ and CD4+ thymocytes that did not adhere to peanut agglutinin (PNA-, which is supposed to represent the mature single positive subset) did not show any age-related change in the proportion of bright and dull cells. Therefore, we concluded that the double positive (CD8+/CD4+, immature, PNA+) thymocytes display reduced expression of CD8 and CD4 antigens with aging. The implications of these findings to the fundamental mechanisms of immunosenescence are discussed.

Aging↗
PubMed1992

Natural cytotoxic cell activity in the snake Psammophis sibilans.

Thymocytes, splenocytes and peripheral blood mononuclear cells (PBMC) of the snake Psammophis sibilans consistently killed the human erythroleukemic cells K562 in a 4 h assay as judged by lactate dehydrogenase enzyme release. PBMC and splenocyte natural cytotoxicity (NC) increased proportionally with increase in the effector/target cell ratio. Spontaneous killer cell activity was consistently 2-3 times higher in peripheral blood (PB) than in spleen. On the other hand, thymocytes displayed low, yet detectable, NC. In an attempt to define the cell subpopulation responsible for natural killer (NK) activity, PBMC were depleted of macrophages or B lymphocytes before use in NK cell assays against K562 cells. Depletion of macrophages did not impair NK activity thus suggesting that macrophages do not mediate spontaneous lysis in the present 4 h assay. Conversely, removal of B lymphocytes by panning onto dishes coated with monoclonal antibody against snake Ig significantly reduced, but did not eliminate, PBMC spontaneous cytotoxicity. These data suggest that T, B and perhaps distinct NK cells participate in spontaneous lysis. This suggestion was confirmed by studies of NC in thymus, spleen and PB the year round. Strong NC was detected during spring and autumn when high numbers of leukocytes including T and B cells can be recovered from spleen and PB. Negligible spontaneous cytotoxicity was observed during early and mid-summer and in winter, periods of the year when snakes are thymus-less and contain few T and B cells in peripheral lymphoid organs. These findings, the first to document natural cytotoxic activity in snakes, were discussed in relation to the issue of NK cell identity in vertebrates.

Animals↗
PubMed1992

Identification of the Schistosoma haematobium soluble egg antigens inducing antibody production and/or T cell proliferation in humans.

Soluble antigens were prepared from Schistosoma haematobium eggs collected from urine of 6-16 year-old children with urinary schistosomiasis. The electrophoretic profile of the soluble egg antigen (SEAH) preparation was almost identical to that (SEAh) obtained from UNDP/World Bank/WHO, Switzerland and prepared from S. haematobium eggs retrieved from intestines of infected hamsters. Reactivity of 50 individual patients with S. haematobium in Western blots led to the identification of the SEA protein bands carrying human B cell epitopes. Some, but not all, of these SEA proteins initiated peripheral blood T lymphocyte proliferation in T cell Western assays. These antigens are probably the ones inducing granulomatous response in vivo, and that are responsible for the immunopathology of the disease.

Adolescent↗
PubMed1991

Immunoglobulins of the snake Psammophis sibilans. Studies using a monoclonal antibody.

A mouse monoclonal antibody (mAb) raised against serum immunoglobulins (Ig) of the snake. Psammophis sibilans stained in indirect immunofluorescence a proportion of snake splenic and peripheral blood lymphocytes, whereas it did not react with thymocytes, erythrocytes, brain, heart, lung, liver or kidney cells. The mAb, designated SR-2, combined in enzyme-linked immunosorbent assay (ELISA) with serum proteins of each of 20 individual P. sibilans tested. On Western blots of P. sibilans reduced whole serum proteins, purified Ig, or anti-rat erythrocyte (RRBC) antibodies eluted from glutaraldehyde-fixed RRBC, mAb SR-2 identified two bands of apparent molecular weight (m.w.) of 60,000 and 51,000 daltons. These bands were due to distinct polypeptides and not resulting from heterogeneous glycosylation of a single polypeptide, as they both were readily detected after periodate oxidation or endoglycosidase-F treatment of serum proteins and isolated Ig. MAb SR-2 bound to CNBr-activated Sepharose 4B precipitated from P. sibilans 125I-labeled serum proteins under non-reducing conditions a band that did not enter 7.5 or 9-16% gel and one of about 150,000 daltons. Under reducing conditions, two heavy bands of approximately 63,000 and 50,000 daltons and two light chains of apparent mass 23,000 and 20,000 bands were precipitated. The data presented provide, for the first time, substantial information on the molecular characteristics of snake Ig.

Animals↗
PubMed1991

Peripheral blood lymphocyte subsets in urinary bladder carcinoma patients.

The percentages of pan T (CD3+), T helper (CD4+), T cytotoxic/suppressor (CD8+), B (CD22+) and natural killer (CD57+) cells in peripheral blood lymphocytes of 15 urinary bladder carcinoma patients and in parallel, 10 healthy donors were estimated, using monoclonal antibodies in indirect membrane immunofluorescence. A significant decrease in the percentage of CD3+ lymphocytes and a highly significant decrease in the proportion of CD8+ cells was revealed in urinary bladder cancer patients. This change was accompanied by a significant increase in the CD4/CD8 ratio and in the frequency of CD57+ (HNK-1+) cells. Our data document, for the first time, the complete lymphocyte profile of patients with advanced (T3) urinary bladder carcinoma. The reason and significance of the decline in CD8+ lymphocyte percentage and the increase of CD57+ cells are discussed.

Adult↗
PubMed1990

Functional markers of the major histocompatibility gene complex of snakes.

In optimal seasonal conditions, outbred adult snakes Psammophis sibilans displayed the major immunological functions related, in mammals, to the presence of the major histocompatibility gene complex (MHC). Thus, out of 30 snake random pairs that exchanged skin transplants 72.9% rejected their allograft in an acute or subacute manner. Strongly significant proliferative response was recorded in 67.3% of 168 separate one-way mixed leukocyte reaction (MLR) cultures. Lymphocytes from 6/11 snakes immunized by skin allografting displayed, after secondary stimulation in vitro, cell-mediated lympholysis (CML) in vitro of 51Cr-labeled lymphoblasts derived from the donor snake. Finally, cytotoxic alloantibodies were readily generated after snake priming with skin allograft and blood cells. Snakes did not only exhibit the major cell- and humoral-mediated immune functions, but these functions appeared to be linked with the degree of MLR disparity. Thus, animals with different MLR rejected skin allografts acutely and produced cytotoxic effector cells. In contrast, MLR-identical animals rejected the skin allograft of their partner chronically and failed to produce killer cells in CML. This significant positive correlation between MLR disparity, graft rejection and CML suggests that the responsible antigens are encoded, as in other vertebrates, by the same genetic system, the MHC.

Animals↗
PubMed1990

Blood testosterone level: a season-dependent factor regulating immune reactivity in lizards.

An attempt to study the interaction between testosterone (Ts) and the immune system of the lizard Chalcides ocellatus led to three major findings: 1) Endogenous serum Ts levels in both males and females peak in spring and are minimal during summer; 2) Injection of Ts in either male or female lizards induces significant depletion of lymphoid elements, reduction in serum antibody titers to rat erythrocytes and increase in skin allograft survival; 3) A distinct inverse correlation between endogenous serum Ts levels and lizard immunocompetence is observed from March to September. The data obtained strongly suggested that concentration of circulating Ts is a season-related factor that is critical in defining the immune profile of lizards.

Animals↗
PubMed1988

Age related occurrence of natural agglutinins in the erisilkworm, Philosamia ricini.

Natural agglutinins against human, guinea pig, and rat erythrocytes (RBC) and bacteria Bacillus thuringiensis were readily detected in hemolymph of final instar larvae with resulting titers of 0-9 (log2). Titers were independent of sex and season but varied conspicuously and reproducibly with age. Moreover, response of hemagglutinins to heating varied with age being heat-labile in younger larvae, yet totally resistant to heating for 30 min at 70 degrees C in older ones. Bacterial agglutinins were uniformly resistant at all larval ages. The study thus reveals that the amounts and physico-chemical properties of P. ricini agglutinins change with larval development. Therefore, larval age should be taken into close consideration before reporting on the occurrence and properties of agglutinins in insects.

Age Factors↗
PubMed1988

Primary in vitro stimulation of antibody production by lizard splenocytes.

Single-cell suspensions of adult lizard (Chalcides ocellatus) spleen have been induced, in vitro, to produce a primary immune response. Using rat red cells (RRBC) as antigen and the culture conditions normally used in most vertebrate species but new for reptilia, it has been found that, in vitro at 37 degrees C, lizard spleen cells produce an antibody-forming response optimal at day 10. The response depends on the number of cultured cells and the dose of antigen, and parallels that obtained in vivo. Leibovitz (L-15) medium supplemented with 10% normal adult lizard serum was a satisfactory culture medium. 2-mercaptoethanol (2-ME), an ingredient used in mammalian cell culture, enhanced antibody production in lizard cells.

Animals↗
PubMed1988

Endogenous corticosteroids mediate seasonal cyclic changes in immunity of lizards.

Endogenous corticosteroid (CS) blood levels were radioimmunoassayed in fresh, field-collected lizards Chalcides ocellatus at two week-intervals throughout the four consecutive seasons. These animals were used in parallel to investigate the splenic T and B lymphocyte level, lymphoproliferative responsiveness to concanavalin A and primary antibody production in vitro against rat erythrocytes (RRBC). The recorded data indicated that fully developed splenic lymphoid tissue and powerful immune responsiveness are coincident with a continuously low CS level, and characterize the period from spring through early autumn. On the other hand, the dramatic lymphocytic destruction and impairment of immune reactivity observed in autumn and winter are associated with not only a high, but above all sustained, rise in endogenous CS levels. Apparently, exposure of lizard lymphocytes to comparatively high, yet physiologic, levels of endogenous CS for prolonged periods of time lead to impairment of their immune functions. In support, long-term administration of exogenous hydrocortisone acetate (HC) to "summer" lizards resulted in a high and lasting elevation in blood CS levels that was associated with a considerable depletion of lymphoid elements and abrogation of immune reactivity, exactly as in normal lizards collected from the field in autumn through winter. In addition, pharmacologic inhibition of CS synthesis by administration of metyrapone at the beginning of autumn greatly modulated the lizard lymphocyte response to the autumn-related immunodepression. The study thus strongly suggests that the autumn/winter-dependent immunosuppression in lizards is essentially due to a high and lasting rise in levels of endogenous CS. The results are discussed from the perspective of the role played by CS in mediating the seasonal rhythms that affect reptilian immunity.

Adrenal Cortex Hormones↗
PubMed1987

Concanavalin A responsiveness and interleukin 2 production in the snake Spalerosophis diadema.

Thymocytes and splenocytes (SC) of adult snakes, Spalerosophis diadema, responded to concanavalin A (Con A) in vitro by strong proliferation during the spring and autumn seasons. Con A-mediated mitogenesis was, however, abrogated in summer and winter. Conditioned medium (CM) collected from snake SC cultures stimulated with Con A in spring or autumn could enhance the Con A summer and winter responses and support the proliferation of splenic lymphoblasts. Gel filtration of native CM on Sephadex G-100 revealed the presence of two biologically active peaks of molecular weight 39-42 and 15 KD. However, only one peak of activity corresponding to molecular weight (m.w.) of 14-15 KD was observed when CM was subjected to analysis by sodium dodecyl sulphate gel electrophoresis (SDS-PAGE). The active molecular forms exhibited isoelectric points of 5.5-5.8 and 6.4-6.6. The findings suggest that Con A activation of snake lymphocytes in optimal seasonal conditions is associated with the secretion of a lymphokine analogous to the interleukin 2 (IL 2) of endothermic vertebrates.

Animals↗
PubMed1986

Effect of hydrocortisone on immune system of the lizard, Chalcides ocellatus. III. Effect on cellular and humoral immune responses.

Administration of a single injection of 1.0 mg/g body weight hydrocortisone acetate (HC) to adult lizards, Chalcides ocellatus in summer elicited a high and lasting rise in serum corticosterone and cortisol, peak levels being, however, in the physiologic ranges of 10 micrograms % (2 X 10(-7) M) and 40 micrograms % (1 X 10(-6) M), respectively. Elevation of serum corticosteroid (CS) concentrations by exogenous HC impaired the proliferative capacity of spleen cells in mixed leukocyte reaction (MLR) and significantly delayed skin allograft rejection. In vivo HC also abrogated the primary in vivo and in vitro immune responses of lizards to rat erythrocytes (RRBC). Reactivity to allogeneic cells in MLR, and antibody production against RRBC were, however, recovered when serum CS levels resumed normal, basal values i.e. at three weeks post-HC injection. These data indicate that rise in circulating CS induces severe immunosuppression in lizards.

Adrenal Cortex Hormones↗
PubMed1986

The development of lymphocytes with T- or B-membrane determinants in the lizard embryo.

To study the ontogeny of lymphocytes in the lizard, Chalcides ocellatus antisera were raised in rabbits against thymocytes collected from adult lizards (AATS) or from embryos of stages 40 and 41 (AETS), and against serum immunoglobulins (AGGS). AATS recognized in adult lizards a surface membrane antigenic system (TA) specific to thymocytes and thymus-derived (T-) cells in spleen, and a distinct antigenic entity (Tt) found exclusively on intrathymic lymphocytes. After exhaustive absorption with adult thymocytes, AETS defined a further antigen (TE). On the other hand, AGGS combined with the immunoglobulin (Ig) determinants present in the cytoplasm and surface membrane of lizard presumptive B lymphocytes. Immunofluorescence assays during the development of the T and B lineage showed that TA+ and Tt+ thymocytes increased from 35% at stage 37 to 96% at stage 41, and were exported precociously to the embryonic splenic environment. Embryonic thymocytes were shown to totally lack surface Ig, whereas 40-50% of splenocytes carried cytoplasmic and/or surface membrane Ig determinants. The data revealed further the presence of a subset of splenocytes bearing the specific markers of both T and B cells.

Animals↗
PubMed1986

Proliferative responses of snake lymphocytes to concanavalin A.

Spleen cells (SC) of adult snakes Psammophis sibilans responded to concanavalin A (Con A) in vitro by strong proliferation during the spring and autumn seasons. Con A-mediated mitogenesis was, however, poor in summer and abrogated in winter. Removal of Sephadex G 10-adherent cells from the SC suspensions did not inhibit the lymphoproliferative responsiveness to Con A in spring. This supports the view that the weak responses in summer and winter are essentially due to lack of competent T lymphocytes.

Animals↗
PubMed1985

Mixed leucocyte reaction (MLR) in the snake Psammophis sibilans.

In spring, spleen cells (SC) derived from outbred adult snakes, Psammophis sibilans, proliferated vigorously in mixed leucocyte cultures (MLC), thus indicating that reptiles are endowed with the subset(s) of lymphocytes capable of recognizing and responding to alloantigens. Sephadex G-10- or nylon wool-adherent latex-ingesting cells provided accessory, rather than stimulatory, function in MLC. The data, based on numerous one- and two-way MLR studies, showed that the snake P. sibilans possesses strong lymphocyte-activating determinants (LAD) which, however, appeared not to be extensively diverse, as mutually or unilaterally unresponsive SC combinations were quite often observed. Furthermore, seasonal investigations revealed that the lymphoproliferative response in MLR is considerable only in some months of spring and autumn, being abrogated during the rest of the year. These findings suggest that antigen sharing and environmental conditions greatly restrict the cell-mediated immune potential of snakes.

Animals↗
PubMed1975

Tumour-associated transplantation antigen in sera of rats with large RSV-induced sarcomas.

A factor inhibiting tumour growth in syngeneic hosts was found in the sera of inbred Lewis rats carrying Rous sarcoma virus-induced tumour (RSL). The findings presented here suggest that the serum factor is a tumour-associated transplantation antigen (TATA) shed from the neoplasm into the circulation. All the tumour bearers' sera tested with RSL cells were negative in indirect membrane immunofluorescence;however, on passive transfer into syngeneic rats, they protected the animals against the growth of an RSL tumour inoculum. A similar protective effect was also observed after injection of TATA prepared from RSL cell membranes by solubilization with potassium cholate. When incorporated into Freund's adjuvant, tumour-bearers' sera immunized the animals against a subsequent RSL sarcoma graft. Sera collected from immunosuppressed rats bearing large sarcomas which presumably contain neither tumour-specific antibody nor antigen-antibody complexes, transferred inhibition of tumour growth to syngeneic hosts. Intact immunological reactivity of recipients was a necessary prerequisite for the protective effect of sera, since the passive transfer of an inhibitory serum to immunosuppressed rats did not inhibit tumour growth. We assume that the TATA present in tumour-bearers' serum is released from the growing neoplasm as a result of either cell death or membrane metabolic turnover.

Animals↗