<em>In vivo</em> modulation of thymus-derived lymphocytes with monoclonal antibodies in mice I. EFFECT OF ANTI-THY-1 ANTIBODY ON THE TISSUE DISTRIBUTION OF LYMPHOCYTES.

A procedure is described for the in vivo removal of all detectable T lymphocytes from spleen and lymph nodes in mice. A single intraperitoneal injection of monoclonal anti-Thy-T antibody into mice leads to rapid depletion of functional I cells from peripheral lymphoid organs, but not thymus. The extent of T-celI depletion is dependent on the cytotoxic titre of the anti-Thy-I antibody used. Antibody with a median cytotoxic titre greater than 10⁶ causes the complete removal of cells bearing Thy-I, Lyt-I and Lyt-2 surface antigens from peripheral lymphoid populations in 3 days. Eight days after treatment Thy-I ⁺, Lyt-I ⁺ and Lyt-2⁺ cells begin to reappear in these organs. Splenic B cells, assayed by the expression of surface immunoglobulin (sig) and by mitogenic responsiveness to bacterial lipopolysaccharide (LPS), are not affected by this treatment. The monoclonal anti-Thy-i antibody does not appear to penetrate thymus tissue and bind to thymocytes. Anti-Thy-I antibody, but not F(ab')₂, is required for in-vivo T-cell depletion. These findings indicate that anti-Thy-I antibody causes the removal of Thy-i ⁺ cells from peripheral lymphoid tissue, and as the circulating levels of anti-Thy-I antibody decrease, cells from the thymus repopulate the thymus-dependent areas of the depleted lymphoid organs. [ABSTRACT FROM AUTHOR]