CD4+ and CD8+CD60+CD45RO+IL-4+IFNγ- T Cells Expressing Receptors for Complement Split Product (CSP) C3a, but Not C5a, Are Increased in Blood of Serum IgE+, Compared With Serum IgE- Adults

RATIONALE: CD4+IL-4+ T cells are required for human and murine IgE responses. We reported that CD4+ T cells and CD8+CD60+ T cells and six cytokines (IL-2,4,6,10,12,IFNα,IFNγ) are required for induction of ragweed specific memory IgE responses. Antigen cleaves complement and human CD4+ T cells express receptors for CSP. Receptors for CSP C3a and C5a on CD8+CD60+ T cells have not been reported.

METHODS: CD4+CD3+ and CD8+CD60+CD45RO±CD45RA±IL-4±IFNγ± T cells in blood of serum IgE+ (fluoroimmunoassay) ragweed sensitized (RS) and IgE- nonallergic humans expressing receptors for CSP C3a and C5a (CD88) (n=2-3/group) were determined by flow cytometry. Data expressed as mean % total lymphocytes and % subset.

RESULTS: Blood of IgE+ RS humans contained increased numbers of CD4+ and CD8+CD60+ T cells expressing receptors for C3a (36, 85%, respectively), compared with IgE- nonallergic humans (16, 36%, respectively). Further, in IgE+, but not IgE- humans, both T cell subsets expressed greatly increased C3a receptors/cell (MESF). In IgE+ humans, virtually all CD8+CD60+ T cells were CD45RO+CD45RA- and IL-4+IFNγ-; in IgE- humans they were virtually all IL-4-, with CD45RA+ cells predominating. Neither CD4+ nor CD8+CD60± T cells of either IgE+ or IgE- humans expressed receptors for CSP C5a (CD88) (<1%).

CONCLUSIONS: The presence of receptors for C3a on CD4+ and CD8+CD60+CD45RO+ IL-4+ T cells required for induction of ragweed specific memory IgE responses suggests that C3a may play an important role in induction of these responses.