The H-2 histocompatibility system and lymphocyte adhesion: interaction modulation factor involvement.

The effects of thymocyte interaction modulation factor on the adhesion of mouse allogeneic thymocytes and B-cells are reported. This glycoprotein, produced by short term cultures of thymocytes, has already been described as reducing the adhesion of syngeneic B-cells, leucocytes and macrophages. Adhesion was measured in suspension culture using the collision efficiency method. This paper reports that: 1. In addition to the syngeneic effect of thymocyte IMF in reducing adhesion of certain unlike cell types there is also an allogeneic effect in which an allogeneic T-IMF will diminish the adhesion of a thymocyte population, or still further reduce the adhesion of a B-cell population than would a syngeneic T-IMF. 2. Thymocyte IMFs were prepared from different congenic strains and tested on the adhesion of syngeneic and allogeneic thymocytes. When factor and cells were syngeneic or matched at any H-2 locus except H-2 D there was no effect on adhesion since it remained at the same value as in controls in their own IMF. But whenever factor and cells were mismatched at H-2 D there was a marked diminution in the adhesion of the cells. 3. Antibodies raised against specific thymocyte IMFs could be used to detect the presence of T-IMF binding to the surface of cells by immunofluorescence or immune cytolysis. These systems show that the antibodies against thymocyte IMF can be used to type the H-2 D type of a cell and that these factors are present at the surface of thymocytes and certain other cell types. They confirm that the thymocyte IMF is either in H-2 D product or is closely associated with H-2 D locus in its binding and action. They also show that the T-IMF antigen on non-lymphocytic types is produced by T-cells or thymocytes. 4. The general relevance of these results is discussed in relation to cell recognition phenomena.