SEPARATION OF MULTIPLE GENES-CONTROLLING THE T-CELL PROLIFERATIVE RESPONSE TO IL-2 AND ANTI-CD3 USING RECOMBINANT CONGENIC STRAINS

T lymphocytes of the strain BALB/cHeA exhibit a low proliferative resp onse to IL-2 and a high response to the anti-CD3 monoclonal antibodies , while the strain STS/A lymphocyte response to these stimuli is the o pposite. We analyzed the genetic basis of this strain difference, usin g a novel genetic tool: the recombinant congenic strains (RCS). Twenty BALB/c-c-STS/Dem (CcS/Dem) RCS were used, each containing a different random set of approximately 12.5% of the genes from STS and the remai nder from BALB/c. Consequently, the genes participating in the multige nic control of a phenotypic difference between BALB/c and STS become s eparated into different CcS strains where they can be studied individu ally. The strain distribution patterns of the proliferative responses to IL-2 and anti-CD3 in the CcS strains are different, showing that di fferent genes are involved. The large differences between individual C cS strains in response to IL-2 or anti-CD3 indicate that both reaction s are controlled by a limited number of genes with a relatively large effect. The high proliferative response to IL-2 is a dominant characte ristic. It is not caused by a larger major cell subset size, nor by a higher level of IL-2R expression. The response to anti-CD3 is known to be controlled by polymorphism in Fc gamma receptor 2 (Fcgr2) and the CcS strains carrying the low responder Fcgr2 allele indeed responded w eakly. However, as these strains do respond to immobilized anti-CD3, w hile the STS strain does not, and as some CcS strains with the BALB/c allele of Fcgr2 are also low responders, additional gene(s) of the STS strain strongly depress the anti-CD3 response. In a backcross between the high responder and the low responder strains CcS-9 and CcS-11, on e of these unknown genes was mapped to the chromosome 10 near D10Mit14 . The CcS mouse strains which carry the STS alleles of genes controlli ng the proliferative response to IL-2 and anti-CD3 allow the future ma pping, cloning, and functional analysis of these genes and the study o f their biological effects in vivo.