ABSTRACT
Receptors for Fc region of immunoglobulins (FcR) are reported to be present on spermatozoa, and also detected in seminal plasma, however their function is still not known. Since various changes in sperm membrane architecture during maturation and passage through female genital tract are reported, experiments were conducted to study the membrane fluidity changes in sperm subsequent to ligation of surface FcR with immunoglobulin and its derivatives. This paper reports that interaction with IgG restricts rotational mobility of cell surface proteins and membrane lipids as studied by EPR spectroscopy using spin probes. Decrease in fluidity was much more pronounced in the presence of aggregated IgG due to crosslinking of sperm FcR by aggregated IgG.
Subject(s)
Animals , Cell Membrane/metabolism , Electron Spin Resonance Spectroscopy , Female , Immunoglobulins/metabolism , Male , Membrane Fluidity , Rats , Rats, Wistar , Receptors, Fc/metabolism , Spermatozoa/metabolism , Spin LabelsABSTRACT
A study was undertaken to reveal the role of Fc and C3b receptor of mouse peritoneal macrophages (MPM) in the uptake of radiolabelled immune complexes. Large latticed preformed complexes consisting of human serum albumin (HSA)-anti HSA at equivalence (IC-Eq) and with antibody excess (IC-Ab) were observed to be avidly taken up by resident macrophages unlike small size complexes with antigen excess (IC-Ag). Macrophages elicited by thioglycollate (Tg) showed higher IC-binding capacity while IC-elicited MPM showed reduction in the same when compared to the resident cells. However, complement coated complexes were significantly taken up by these IC-elicited macrophages. Uptake studies were further extended to determine the expression of Fc and C3b receptor activity in MPM when elicited with preformed IC. Tg-elicited MPM were observed to bind greater number of IgG-coated erythrocytes (E-IgG) than resident MPM whereas IC-elicited MPM bound E-IgG poorly. When Fc receptors were blocked by in vitro IC treatment, poor binding of complement coated E-IgG [E(IgG)C] was recorded in resident MPM. The present complement medicated rosetting data tends to show enhanced expression of C3b receptors on IC-elicited macrophages.
Subject(s)
Animals , Antigen-Antibody Complex/metabolism , Endocytosis , Macrophages, Peritoneal/metabolism , Mice , Mice, Inbred BALB C , Receptors, Complement 3b/metabolism , Receptors, Fc/metabolism , Rosette Formation , Serum Albumin/immunology , Up-RegulationABSTRACT
Durante el desarrollo de esta línea de investigación se investigaron aspectos relacionados a la interacción entre complejos inmunes (CI) y receptores celulares para el gragmento Fc de IgG (RFc g). En primer término se demonstró que la vía alternativa del complemento es la principal responsable de la liberación de los Cl unidos a los RFc de células mononucleares periféricas humanas. Este mecanismo regulador fue estudiado a travées de la recuperción funcional de la citotoxicidad celular dependiente de anticuerpos (CCDA), reacción muy sensible a la inhibición por Cl. Los resultados sugieren, al menos en parte, que los niveles de Cl circulantes no necesariamente están relacionados en forma directa con el daño producido por los mismos. Por otro lado, se demonstró que la ciclofosfamida (Cy), droga de amplio uso en el tratamiento de enfermedades que cursan con Cl, es un eficiente amplificador de la depurción de Cl particulados, a través de la activación del sistema mononuclear fagocítico. Finalmente, se demonstró que los Cl son capaces de mediar efectos citotóxicos inespecíficos hacia diferentes células "blanco", a través de la inducción de la liberación de intermediarios reactivos del O2