Since the introduction of the hybridoma technique by KShler and Milstein (1975), a more precise serological and biochemical analysis of complex antigenic systems has become possible, and additional mouse alloantigen systems were revealed (Lemke et al. 1979, Kimura et al. 1980, 1981, Tada et al. 1980, 1981a). The discovery of new Ly alloantigens by use of monoclonal antibodies led us to interesting evidence that the genes encoding cell surface alloantigens are clustered together (Tada et al. 198 lb). The Ly-ml0 (formerly called Ly-10, Kimura et al. 1980) is one such example, i. e., Ly-mlO and Lyt-I loci are closely linked with each other. The present report determines the precise distance between Ly-m10 and Lyt-1 loci and provides some evidence relating to the gene control of Ly-ml0 alloantigen.
Our previous data showed Ly-ml0.1-specific antibody to react with lymphocytes of C57BL/6-Lyt-1 a mice and not with C57BL/6 mice, indicating a close linkage between Lyt-i and Ly-ml 0 loci. To confirm this linkage and to measure the precise distance between these two loci, two separate segregation analyses were performed. First, expression of Ly-mlO alleles (Ly-ml0.1 + versus Ly-ml0.1-) and Lyt-1 alleles was tested by direct cytotoxicity assay in two sets of recombinant inbred (RI) strains, BXD and AKXD (Taylor et al. 1975, Jenkins et al. 1981), obtained from the Jackson Laboratory (Bar Harbor, Maine). Monoclonal antibodies against Lyt-l.1 and Ly-ml0.1 were derived from the hybridoma clones W3 and $3.214, respectively (Kimura et al. 1980). (The hybridoma lines used in this study are available to interested investigators.) Conventional anti-Lyt-l.2 alloantiserum was raised by immunizing C3H/An mice with the thymocytes of C3H-CE-Lyt-l.2 strain according to the protocol of Shen (Shen 1977). As shown in Table 1, there are two recombinants among 25 BXD RI strains and two recombinants among 25 AKXD RI strains. The estimate of recombination frequency between Lyt-1 and Ly-mlO loci using the Haldane and Waddington (1931) equation is 0.023