Two separate functions of class II (Ia) molecules: T-cell stimulation and B-cell excitation.
We have evaluated the role of major histocompatibility complex-encoded class II (Ia) molecules as transmembrane signaling receptors in the T helper cell-dependent activation of B lymphocytes. For these studies, we utilized the murine B-cell lymphoma CH12, which expresses both I-A and I-E class II molecules. In addition, CH12 cells carry IgM of known antigen specificity and require both specific antigen and Ia-restricted T-cell help for the induction of antibody secretion. In this respect, they resemble normal resting B cells. We have studied the ability of antigen-specific or alloreactive T helper cells reactive with either the I-A or the I-E molecules on CH12 to be activated and their ability to stimulate antibody production by CH12. The results show that, although CH12 cells present antigen to T helper cells that interact with either the I-A or the I-E molecules, CH12 cells are stimulated to secrete antibody only by T helper cells reactive with their I-E molecules. Our data demonstrate that class II molecules are transducers of signals for B-cell excitation in addition to serving a restricting function for helper T-cell stimulation. Moreover, the data demonstrate that these two functions, T-cell stimulation and B-cell excitation, are discrete and need not be expressed by the same Ia molecule.
Corley
R B
RB
LoCascio
N J
NJ
Ovnic
M
M
Haughton
G
G
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D002999:Clone Cells / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000502:physiology*; D008223:Lymphoma / Q000276:immunology; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology
D000949:Histocompatibility Antigens Class II