Lymphoid source and target of murine leukocyte adherence inhibition factor (LAIF)

The cellular source of murine LAIF detected by an indirect leukocyte adherence inhibition (LAI) assay using capillary tubes was investigated using non-inducing peritoneal cells (PC) from normal and spindle-cell sarcoma-bearing A/J mice. Cell populations containing greater than 95% T-cells, B-cells or macrophages were prepared from PC using a series of elimination and enrichment procedures. The in vitro incubation of enriched T-cell populations (less than 0.05% macrophages) from tumor-bearing mice with the specific soluble tumor antigen did not result in the release of detectable levels of LAIF; however, the addition of 10% normal isologous macrophages to the T-cells resulted in a significant release of LAIF. Enriched B-cell populations did not release LAIF either by themselves of when 10% normal isologous macrophages were added. Cell populations containing both T-cells and B-cells produced significant levels of LAIF, but only when suitable numbers of macrophages were present. Treatment with anti-Thy-1.2 alloantiserum and complement resulted in the abrogation of LAIF production by mixed cell populations. Using Lyt-1.2 and Lyt-2.2 alloantisera and complement to prepare either Lyt-1.2 or Lyt-2.2 depleted T-cell populations, it was found that the Lyt-1.2 subpopulation was responsible for the release of LAIF in this test system. LAIF was found to be effective in reducing the glass adherence of macrophages but not of T-cells or B-cells.