Early and late primary IgM antibody responses of mice to Thy-1.1 antigens showed different antigenic and cellular requirements. We studied genetic controls of the early primary responses, which could be induced by subcellular thymocyte antigens independently of host T-cell activity. All Thy-1.2 mouse strains of Igha(BALB/c and BC8), Igh-VaCb(BAB14), Ighd(AKR/Cum), Ighj(CBA/J, C3H/HeN, C3H.SW, and C3H.JK), and Ighn(NZB) definitely responded early to Thy-1.1 antigens from AKR/J (Ighd), A.Thy-1.1 (Ighe), or B10.Thy-1.1 (Ighb) mice or SD rats, whereas all strains of Ighb(C57BL/6, C57BL/10, B10.D2, B10.BR, B10.A, CB20 and CWB), Ighc(DBA/2), Ighe(A/J), and Igho(C.AL20) responded poorly to the same antigens. This contrasts with the observation that both strains of Ighj(C3H/HeN) and Ighb(B10.BR) responded well at later times. As was the case for late responses, the matching of H-2 between donor and recipient resulted in early responses of exceptional quality in high-responder strains. It was concluded that under the influence of H-2, whose incompatibility between donor and recipient partially interferes with responses, early but not late primary Thy-1.1-specific antibody responses are selectively controlled by Igh-V or closely linked Ir gene(s) as a new VHmarker.
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