Sequential activity of gamma-delta T-cell receptor bearing lymphocytes, specific T-cell factors, and alpha-beta T-cell receptor bearing T-cells: a hypothesis.

The cell-mediated immune response against cell-bound antigens are biphasic responses. The 'classical' components of cell-mediated immunity such as delayed type hypersensitivity (DTH) and cytotoxic T-cells, are preceded by antigen-specific T-cell factor production. These antigen-specific T-cell factors can be detected in the serum 1-2 days after immunization, which suggests that these antigen-specific T-cell factors play an important role in the initiation of cell-mediated immune responses. Factor-producing lymphocytes can be detected already 1 day after immunization at the site of the antigen challenge, and at first 4-5 days after immunization in the peripheral lymphoid organs. The phenotype of these factor-producing lymphocytes is Thy-1+, CD3+, L3T4 (CD4)-, Lyt2 (CD8)-, whereas the T-lymphocytes inducing the DTH response are Thy 1+, CD3+, L3T4 (CD4)+, Lyt2 (CD8)-. This suggests that these factor-producing lymphocytes are gamma-delta bearing T-lymphocytes. gamma-delta TCR bearing T-cells can develop independently of the thymus, and are present in athymic nude mice. Immunization of athymic (nude) mice induces antigen-specific T-cell factor production as well. This suggests that the gamma-delta bearing T lymphocytes present in nude mice can react to cell-bound antigens and produce these factors.