Specific T-cell factors that initiate cellular immune responses are produced by CD4-, CD8-, V beta 8- lymphocytes and are present in nude mice.

The antigen-specific suppressor inducer T-cell factors (TsiF) specific macrophage-arming factor (SMAF) and mast cell-arming T-cell factor (MTCF) are produced by lymphocytes that have a Thy 1+, Lyt-1+, CD4-, CD8-, and V beta 8- phenotype. The SMAF- and MTCF-producing lymphocytes are positive for the monoclonal antibody (mAb) 14-30, which is directed against TsiF and also binds SMAF and MTCF. The SMAF-producing lymphocytes are negative for mAb 14-12, which is directed against suppressor effector T-cell factors. The MTCF-producing lymphocytes are probably CD3+. The CD3 phenotype of SMAF-producing lymphocytes could not be established in the biological assays. Lymphocytes mediating the classical (24 hr) delayed-type hypersensitivity (DTH) response are Thy 1+, CD3+, CD4+, CD8-, V beta 8+. SMAF- and MTCF-producing lymphocytes were also detected in congenitally athymic (nude) mice. We conclude from these results that (i) the subset of lymphocytes (CD4-, CD8-, V beta 8-) that produces SMAF and MTCF (and is involved in the initiation of the cellular immune response) is different from the subset (CD4+, V beta 8+) that exerts effector functions, like DTH or cell-mediated immunity. (ii) In case of a CD3+ phenotype of SMAF- and MTCF-producing lymphocytes, this CD3+, CD4-, CD8- phenotype together with their presence in nude mice suggests that these lymphocytes may bear a gamma delta T-cell receptor (TCR), although an alpha beta TCR positive phenotype cannot be excluded. (iii) Since SMAF- and MTCF-producing lymphocytes bind mAb 14-30, these TsiF can be associated with the plasma membrane of the lymphocytes by which they are produced.