[Role of LFA-1/ICAM-1 in the activation of murine thymocytes stimulated by Con A]

The biological significance of the signals triggered by the interaction of cell surface expressed LFA-1 and ICAM-1 has been investigated in Con A stimulated murine thymocytes. Addition of anti-LFA-1 or/and anti-ICAM-1 McAb to the thymocyte culture in the presence of Con A, the cell proliferation was profoundly inhibited. Such inhibitory effect was more significant by the addition of anti-LFA-1 than by the addition of anti-ICAM-1 McAb. FACS analysis revealed that the proliferation of CD8+ T cells was more sensitive to the inhibitory effect of anti-LFA-1 McAb than did the proliferation of CD4+ T cells. The anti-LFA-1 McAb imposed inhibitory effect, however, could be reversed by the supplementation of IL-2 in the initiation of the culture. The proliferation of cultured Con A activated T blast cells could no longer be inhibited by the addition of anti-LFA-1 McAb. Furthermore, neither anti-LFA-1 nor anti-ICAM-1 McAb could block PMA+A23187 induced thymocyte proliferation. The results imply that the ligand-receptor pair of LFA-1-ICAM-1 molecules also takes part in the early events of Con A activated signal transduction pathway which leads to the proliferation of thymocytes.