Cellular and genetic control of antibody responses in vitro. II. Ir gene control of primary IgM responses to trinitrophenyl conjugates of poly-L-(Tyr,Glu)-poly-D,L-Ala--poly-L-Lys and poly-L-(His,Glu)-poly-D,L-Ala--poly-L-Lys.

The in vitro primary IgM anti-hapten responses to trinitrophenyl (TNP) conjugates of poly-L-(Tyr,Glu)-poly-D,L-Ala-poly-L-Lys (T,G)-A--L and poly-L(His,Glu)-poly-D,L-Ala--poly-L-Lys (H,G)-A--L were shown to be T-cell dependent and under autosomal dominant H-2-linked Ir gene control which mapped within the K or I-A regions of the H-2 complex. The in vitro response to TNP-keyhole limpet hemocyanin, while T-dependent, was not under demonstrable genetic control. The genes governing the in vitro primary IgM anti-hapten responses to TNP-(T,G)-A--L and TNP-(H,G)-A--L resemble the Ir genes controlling the in vivo secondary IgG responses to (T,G)-A--L and (H,G)-A--L in that they are autosomal dominant, map identically within the H-2 complex, and have identical responder and nonresponder haplotypes. It is concluded that Ir genes can govern the ability to generate an IgM response upon initial exposure to antigen.