The B region-associated antigens and MLR phenotypes in the Japanese inbred strains of rats.

Seven different alloantisera absorbed with red blood cells (RBC) from appropriate strains of rats detected a series of B cell alloantigenic specificities that could be divided into two groups, presumably coded for by at least two different closely-linked loci in the rat major histocompatibility complex (MHC), RT1. The one locus had two allele codes for a broad specificity and the other locus codes for a unique specificity that was found only in the restricted strains of rats that shared the same mixed lymphocyte reaction (MLR) phenotype. RBC-absorbed alloantisera were monitored against a panel of B cell fractions obtained from sixteen inbred strains. Two alloantisera, ACI anti-W and W anti-TO detected two broad specificities, into either of which all inbred strains tested were classified. Two broad RT1-B region-associated specificities were thus designated provisionally as Ba-1.1 and -1.2. Another five alloantisera detected four respective specificities which have a narrower strain distribution. Sixteen inbred strains were classified into one of five specificities detected by W and F344, F344 anti-SDJ, WKA anti-ACI, W anti-BUF and ACI anti-W absorbed with LEJ lymph node cells. Each specificity was designated provisionally as Ba-2.1, -2.2, -2.4, -2.6, -2.7, respectively. A complete association of Ba-2 specificities with MLR phenotype was observed. Antigenic specificities of Ba-2.2, -2.2 and -2.4 were all classified in a group of Ba-1.1 specificity, whereas Ba-2.6 and -2.7 specificities were associated with Ba-1.2 specificity. This relationship suggested a linkage disequilibrium between the two loci for the Ba antigens.