PURIFIED EXCRETORY-SECRETORY COMPONENT OF FILARIAL PARASITE ENHANCES FC-EPSILON-RII CD23 EXPRESSION ON HUMAN SPLENIC B-CELLS AND T-CELLS AND IGE SYNTHESIS WHILE POTENTIATING T-HELPER TYPE 2-RELATED CYTOKINE GENERATION FROM T-CELLS/

The CD23-bearing cells are known to be involved in multiple biological activities, including IgE synthesis and IgE-dependent cytotoxicity to parasites. The factors that regulate interleukin-4 (IL-4)induced IgE synthesis in helminthic infection were analysed by using an excretory- secretory component (ESC) of Dirofilaria immitis (DI). Human splenic B and T cells significantly enhanced the expression of low-affinity Fc receptors for IgE (Fc epsilon RII/CD23) by stimulation with ESC, eithe r acting alone or in synergy with IL-4. On B cells, ESC potentiated th e CD23 expression in synergy with IL-4, whereas ESC alone was unable t o modulate CD23 expression. In contrast, ESC directly induced CD23 exp ression on T cells by acting alone and no further enhancement was obse rved in the presence of IL-4. Furthermore, IL4-induced IgE synthesis b y splenic mononuclear cells (SMNC) was greatly enhanced in the presenc e of ESC. Of particular interest, T cells primed by ESC significantly produced a set of cytokines including IL-3, IL-4, IL-5 and IL-6. Inasm uch, IL-4-induced IgE synthesis in helminthic infection may be selecti vely modulated by parasite protein(s) acting on the generation of T-he lper type 2 (Th2)-related cytokines.