Covalent association between human thymus leukemia-like antigens and CD8(Tp32) molecules.

Several TL-like molecules have been identified on human thymocytes. Some of these TL-like molecules are disulfide-bonded to CD8(Tp32), on which they form the thymus-specific 45 kilodalton (Kd) subunit of the CD8 complex. TL-like molecules are associated with beta 2 microglobulin. However, beta 2 microglobulin is not co-precipitated with the CD8-TL complexes, suggesting that CD8 and beta 2 microglobulin are alternative association structures for TL-like molecules. CD8 is present as high m.w. complexes of 72 and 135 Kd that are composed of 32 Kd subunits only, and as high m.w. complexes of 120 and greater than 150 Kd that are composed of both 32 and 45 Kd (TL-like) subunits. A third subunit of CD8 with an apparent m.w. of 52 Kd was seen as part of the 72 Kd complex, and may represent an incompletely reduced dimer of the 32 Kd subunit.