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At least 991 records · Page 55Linked to original sources
PubMed1975

Cytolytic lymphocytic cells with complement receptor in human blood. Induction of cytolysis by IgG antibody but not by target cell-bound C3.

Human blood lymphocytes were fractionated on glass bead columns charged with sheep erythrocyte (Es) membranes-bearing human C3b (7,000-10,000 molecules/Es). In the passaged cells the proportion of C receptor lymphocytes was strongly reduced, in parallel with the capacity to lyse chicken erythrocytes (Ec) in the presence of IgG-rabbit anti-Ec antibody. In other experiments, lymphocytes forming rosettes with Es bearing activated rabbit complement [C(ra)] from C6-deficient rabbits were removed by centrifugation through human serum albumin-gelatine mixtures. This procedure also depleted the lymphocyte preparations of antibody-dependent cytolytic effector cells. The results suggest that rations of antibody-dependent cytolytic effector cells. The result suggest that such effector cells have receptors for human C as well as for C(ra). Lymphocytes were not able to lyse erythrocytes bearing either human C3b (similar to 30,000 molecules/Ec) or activated C(ra) in the absence if IgG antierythrocyte antibodies. Under the same experimental conditions these target cells were efficiently lysed in the presence of small amounts of IgG antitarget cell antibodies. This suggests that the interaction between the cellular Fcreceptors and the Fc part of the inducing antibodies is of special significance for the triggering of the cell-mediated lytic reaction. However, although target cell-bound C did not trigger cytolysis, it seemed to potentiate antibody-dependent cytolysis, probably by enhancing effector cell-target cell contacts.

Animals↗
PubMed1977

T lymphocytes bearing complement receptors in a patient with chronic lymphocytic leukaemia.

A patient is described who presented with a disease clinically resembling chronic lymphocytic leukaemia, characterized by generalized lymphadenopathy, pleural and peritoneal effusions, a blood lymphocyte count of 700,000/mul and failure to respond to conventional therapy. At least 95% of these cells formed rosettes with sheep erythrocytes (E) and with erythrocytes coated with 19S antibodies and complement (EAC). All of these cells bound rabbit anti-human thymocyte serum; this serum bound to 0--22% of the lymphocytes from twenty other patients with chronic lymphocytic leukaemia. These unusual cells did not bear surface immunoglobulin detectable by immunofluorescence. The clinical and cellular features of this malignancy are compared to previously reported cases of T cell chronic lymphocytic leukaemia. As this case illustrates, T-cell chronic lymphocytic leukaemia may present without skin lesions and may be a more aggressive disease than the more common B-cell neoplasm.

Cell Membrane↗
PubMed1993

Ligand specificity of purified complement receptor type three (CD11b/CD18, alpha m beta 2, Mac-1). Indirect effects of an Arg-Gly-Asp (RGD) sequence.

We have purified CR3 to homogeneity by affinity chromatography on C3bi-Sepharose and elution with EDTA. C3bi-coated erythrocytes bound to this purified CR3, and binding was dependent on the concentration of both C3bi and CR3, as well as on temperature and the presence of divalent cations. Moreover, binding could be blocked by mAb against CR3 or C3bi and could be enhanced by the addition of integrin modulating factor-1. We used the purified CR3 to test whether several putative ligands of CR3 directly bound the receptor. The interaction of purified CR3 with fibrinogen, filamentous hemagglutinin of Bordetella pertussis, lipophosphoglycan and glycoprotein 63 of Leishmania mexicana, and lipopolysaccharide from Escherichia coli was confirmed. However the interaction of CR3 with zymosan or its major component, beta-glucan, was not observed in these assays. Previous studies showed that binding of C3bi to PMN could be blocked with Arg-Gly-Asp (RGD) containing peptides and were interpreted to indicate that the RGD sequence in C3bi interacts directly with CR3. We found, however, that RGD containing peptides were unable to block the interaction of C3bi with purified CR3, yet retained the ability to block binding of C3bi to cells. We conclude that RGD-peptides do not directly bind CR3, but instead indirectly effect CR3 function. Inasmuch as the effect of RGD-peptides could be mimicked with antibodies against leukocyte response integrin, we suggest that RGD-peptides may bind to leukocyte response integrin on polymorphonuclear leukocytes and influence CR3 activity via this receptor.

Amino Acid Sequence↗