The hybridoma produced by the fusion of
lactate dehydrogenase-B (
LDH-B)-primed B10.A(2R) mouse suppressor T (Ts) cells with the BW5147
thymoma secretes two kinds of
T suppressor factors (
TsF),
TsF-A and
TsF-E. The
TsF-A suppresses A beta-restricted and the
TsF-E, E beta-restricted helper T (Th) cells. Each of the two factors consists of two
polypeptide chains, an
antigen-binding chain (ABC) and a major histocompatibility complex (MHC) chain. The ABC binds
LDH-B, which is then recognized by one of the two receptors of the Th cell and an
antigen bridge is formed between the factor and the Th cell. This chain is presumably identical in both factors. The MHC chain of the
TsF-A carries
antigenic determinants recognized by three sets of
monoclonal antibodies:
antibodies specific for the A beta chain,
antibodies specific for class II determinants expressed in T cells and controlled by the A beta-E beta chromosomal segment, and
antibodies crossreacting with J determinants. The MHC chain of the
TsF-E carries determinants recognized by E beta-specific and by J-specific
antibodies. Only some of these serologically detectable determinants reside in the region of the
TsF molecule recognized by Th cells. These findings suggest that the J determinants are carried by the modified E beta and also by the modified A beta chains.