Immune response to the H-X antigen on P815-X2. I. Recombinant inbred strain analysis and lack of effect of castration.

In a preceding report, the detection of an H-2-linked immune response to the H-Xd antigen on the P815-X2 mastocytoma was demonstrated by the significantly increased survival of (C57BL/6 X DBA/2)F1 (B6D2F1) male hybrids (H-Xb) compared with female siblings (H-Xb/H-Xd) after injection with the histocompatible tumor (H-Xd). This interpretation was supported by the absence of this sex effect in reciprocal D2B6F1 hybrids (H-Xd and H-Xd/H-Xb). Additional findings presented in this paper support the conclusion that this sex effect is due to a true immunological response to H-Xd: (a) Reciprocal (DBA/2 X C57BL/6 H-2 mutant)F1 hybrids, as well as D2B6F1, failed to exhibit the sex effect: (b) the demonstration of the sex effect in (BALB/c X DBA/2)F1 and (BALB/c-H-2dm2 X DBA/2)F1 hybrids and in (C57BL/10 X DBA/2)F1 hybrids was consistent with the known H-X incompatibilities between the strains BALB/c and DBA/2 and C57BL/10 and DBA/2, respectively, previously demonstrated by skin grafting; and (c) the sex effect was not abrogated by castration of male B6D2F1 hybrids. Variability in the presence or absence of the sex effect was observed in various [recombinant inbred (RI) X DBA/2]F1 hybrids and may be attributed to the influence of a regulatory non-H-2 gene which is closely linked to the gene coding for mouse kidney-androgen-regulated protein (KAP) but androgen-independent, or to variability in inheritance of the H-Xb allele among the RI lines. It is proposed that the P815-X2 model may be utilized to type RI lines derived from a cross between C57BL/6 and DBA/2 for their H-X genotypes.