CD3+ T cells in severe combined immunodeficiency (scid) mice. VI. Rescue of scid-derived, IgM-producing B cells by transfer of CD4+ CD8- T cells from various lymphoid organs.

Intravenous injection of purified CD4+ CD8- T cells from thymus, spleen or lymph nodes of adult dm2 donor mice (H-2d, Ld-, IgMa) into young C.B-17 scid/scid (scid) mice (H-2d, Ld+, IgMb) partially and selectively reconstituted the splenic CD4+ T-cell compartment of recipient scid mice. This was demonstrated by cytofluorographic analyses, histological examinations, growing donor-derived CD4+ T-cell lines in vitro from spleens of transplanted scid mice, and serial passage of Ld-, CD3+CD4+CD8- T-cell lines through young scid recipients for more than 1 year. Host-derived IgMb appeared in sera of all CD4+ T-cell-transplanted young scid mice, while none of the sex- and age-matched, non-transplanted control scid mice was Ig+. B-cell leakiness was most efficiently induced by transfer of low numbers of adult CD4+ CD8- thymocytes: transfer of 10(3) purified CD4+ CD8- thymocytes efficiently rescued scid-derived B cells, while transfer of 2 x 10(7) non-fractionated thymocytes from the same donor mouse was inefficient. Serum antibodies of scid mice with T-cell-induced B-cell leakiness stained congenic 'double-positive' (CD4+ CD8+) thymocytes and immunoprecipitated protein bands with an apparent MW of 14,000, 28,000, 43,000, 65,000 and 80,000 from 125I-labelled thymocytes. These data indicate that repopulation of peripheral lymphoid organs with CD4+ T cells is always accompanied by partial co-reconstitution of the B-cell system, and raises the question of the interdependence of these two lymphocyte subsets.