RESUMO
Purified IgG from BALB/c mouse anti-C3H serum exerts positive inotropic and chronotropic effects in C3H mouse atria and induces testosterone synthesis in C3H mouse Leydig cells. The effect depends on IgG concentration and can be abolished by beta-adrenergic-receptor and luteinizing hormone-receptor antagonists. IgG interferes with the binding of dihydroalprenolol and luteinizing hormone. Monoclonal antibodies against major histocompatibility complex class I antigens were active on the Leydig cells of C3H and BALB/c mice. There was a parallelism between the effect of each individual monoclonal antibody with specificity for a particular haplotype and the response of the target cell from the strains carrying such haplotypes. These antibodies could precipitate the soluble luteinizing hormone-receptor complex. The results suggested that bound hormone triggers the association of major histocompatibility class I antigen with the receptor, thereby activating the respective target cells.
Assuntos
Antígenos de Histocompatibilidade , Receptores Adrenérgicos beta/fisiologia , Receptores do LH/fisiologia , Animais , Anticorpos Monoclonais/fisiologia , Função Atrial , Membrana Celular/fisiologia , Gonadotropina Coriônica/metabolismo , Di-Hidroalprenolol/metabolismo , Frequência Cardíaca , Antígenos de Histocompatibilidade/imunologia , Soros Imunes , Imunização , Alótipos de Imunoglobulina , Imunoglobulina G/fisiologia , Técnicas de Imunoadsorção , Isoproterenol/farmacologia , Células Intersticiais do Testículo/imunologia , Células Intersticiais do Testículo/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Contração Miocárdica , Propranolol/farmacologia , Receptores do LH/imunologia , Testosterona/biossínteseRESUMO
We studied the involvement of major histocompatibility (MHC) class I antigens on the mechanism of LH/hCG receptor activation. For this purpose we investigated the effects of anti-MHC class I antibodies on hormone-receptor interaction, signal transduction, and MHC class I antigen-receptor interaction. Monoclonal antibodies against MHC class I antigen were able to stimulate testosterone production in mouse Leydig cells with the same potency as LH. This biological effect depends on the concentration of antibody used and could be abolished by a LH antagonist. There is a perfect parallelism, for each monoclonal antibody, between the specificity for a particular haplotype and the response of the target cells from the strains carrying such a haplotype. The same antibodies were able to precipitate the soluble LH/hCG receptors, as both a hormone-receptor complex and a free receptor. The results suggest that bound hormone triggers an association of the MHC class I antigen with the LH/hCG receptor, resulting in activation of the target cell.