Antigen presentation and assembly by mouse I-Ak class II molecules in human APC containing deleted or mutated HLA DM genes

Abstract

The behavior of mouse I-Ak molecules was studied in the human Ag presentation mutants T2 and 9.5.3, which contain deleted or mutated HLA DM genes. HLA class II molecules expressed by these APC are defective in presentation of native Ag and are mostly complexed with class II-associated invariant chain peptides (CLIP). In contrast to human class II molecules, a significant proportion of mouse I-Ak molecules expressed in T2 and 9.5.3 were associated with antigenic peptides, indicating that I-Ak/peptide assembly is possible in the absence of the Dm proteins. Thus, the presentation of determinants derived from hen egg lysozyme (HEL), keyhole limpet hemocyanin, and conalbumin was normal in 9.5.3Ak..