Biomedical subjects

R el Ridi

Publications and source records attributed to R el Ridi.

8 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↗

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↗