T-cell-dependent B-cell stimulation is H-2 restricted and antigen dependent only at the resting B-cell level.
Cloned lines of helper thymus-derived (T) cells produce help for bone marrow-derived (B) cell growth and Ig secretion in the presence of histocompatible adherent cells and of specific antigen. This help stimulates histocompatible as well as histoincompatible B-cell blasts polyclonally. Thus, neither antigen nor histocompatibility, but antigen-unspecific factor(s) for growth and Ig secretion are required to stimulate a B-cell blast through the next round of division. On the other hand, only histocompatible, resting, small B cells, and only those binding their specific antigen, can be stimulated by antigen-activated T-cell help to initiate growth and Ig secretion. The preference of the resting B cells for such collaboration with T-cell help is mapped to the K end of the H-2 histocompatibility locus, and probably constitutes the antigen expressed on B cells by the immune response (I) region. It appears that a resting B cell is excited by the binding of specific antigen to surface Ig and by the interaction of its surface Ia antigen with helper T cells. After this dual recognition the excited B cell can be stimulated by the antigen-unspecific factor(s) generated by the interaction of helper T-cells, adherent cells, and antigen to initiate replication.
D000818:Animals; D000917:Antibody Formation; D000941:Antigens; D001402:B-Lymphocytes / Q000276:immunology*; D006183:H-2 Antigens; D007075:Immunoglobulin M / Q000096:biosynthesis; D007519:Isoantigens; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology*
D000941:Antigens; D006183:H-2 Antigens; D007075:Immunoglobulin M; D007519:Isoantigens