Phosphorylation of signaling molecules in the proximal TCR signaling pathway is impaired in nasal polyp-derived T cells. Compared to CD45RO + T cells from normal donor PBL, polyp-derived CD45RO + T cells show decreased phosphorylation of ZAP70 (1.8 versus 2.8, n = 4, p < 0.05), SLP-76 (3.0 versus 6.1, n = 4, p < 0.05), Lck (1.9 versus 3.0, n = 4, p < 0.05) and CD3ζ (1.6 versus 5.6, n = 3, NS) following stimulation with anti-CD3/CD28, as measured by change in mean fluorescence intensity. Independent experiments comparing normal donor peripheral blood T cells (closed symbols) to polyp-derived T cells (open symbols) are represented by different symbols, and means are represented by horizontal lines.