Further polymorphism of the Tla locus defined by monoclonal TL antibodies

Six new monoclonal TL antibodies are described. At least one new TL antigen is defined (TL.7), and at least one more Tla allele, bringing the total number of known Tla alleles to six. Five of the monoclonal antibodies, and probably all six, identify distinct TL antigenic specificities. Four of these antigens conform in strain distribution and expression on leukemia cells to antigens defined by conventional antisera. The data contain a hint that monoclonal TL antibodies like TL.m6 may serve to identify a region of the Tla gene, which determines whether or not prothymocytes will respond to physiological induction by expressing TL, and thus may provide a means to study the regulatory mechanism that determines whether mouse strains are phenotypically TL+ or TL-.