Selection of a broad repertoire of CB4(+) T cells in H-2Ma(0/0) mice

According to past reports, H-2Ma(0/0) mice express a single major histocompatiblity complex class II molecule, A(b), heavily loaded with a single peptide derived from the invariant chain, CLIP. Despite the highly restricted diversity of the class Il:peptide complexes expressed on thymic stromal cells in the mutant animals, a large and diverse population of CD4(+) T cells is positively selected. However, two important issues remained unresolved and al are addressed here: Just how preponderant is CLIP occupancy of the class II molecules from H-2M(0/0) mice? How extensive and functionally competent is the CD4+ population selected in the mutant animals? Our results argue that a single class il:peptide complex can select a very broad, though not complete, repertoire of CD4+ T cells.