Epitopic Groups of CD1 Molecules

The first cluster of differentiation, CD1 [Thy, gp45, 12], defined by the First International Workshop on Human Leucocyte Differentiation Antigens (1) included antibodies NA1/34, T6, D47, and M241. The antibodies reacted with thymocytes, but not peripheral T cells, with some T-ALL cells from both children and adults, and with some T-lymphoid cell lines. Antibodies D47 (2) and M241 (3) particularly were dissociated from NA1/34 (4) and T6 (5) in, respectively, T-ALL cells from adults and T-ALL cells from children. Biochemically all of the CD1 antibodies recognize a structure which is similar to that of human HLA-class I molecules with approximately 45,000-M r heavy chains attached to β2-microglobulin.