THE CD4(-LYMPHOCYTE IS A SITE OF STEROID RESISTANCE IN ASTHMA() T)

Phytohaemagglutinin (PHA)-induced T-cell proliferation is suppressed c ompletely in steroid-sensitive asthma (SSA) by fluticasone propionate (FP). By contrast, in patients with steroid-resistant asthma (SRA), th is proliferative response is only partially attenuated by steroids, wh ich suggests that the T lymphocyte may harbour a key molecular defect in these patients. Both CD4(+) and CD8(+) T cells may be involved in o rchestrating the inflammation underlying asthma. We examined whether C D4(+) or CD8(+) T cells isolated from SRA and SSA patients are equally susceptible to steroid suppression of PHA-induced proliferation. Comp lete suppression of CD4(+) T-lymphocyte proliferation was seen in both SSA and control subjects at concentrations of 10(-9) M FP. In contras t, proliferation of CD4(+) T cells from SRA patients was only partiall y inhibited, even at 10(-6) M FP. CD8(+) responses from SRA, SSA and c ontrols were all similar, with only a partial suppression of prolifera tion at 10-6 M FP. Differential suppression by FP of CD4(+) T cells ha s thus been demonstrated between SRA and SSA patients.