Imbalance of CD4+ lymphocyte subsets in patients with mixed connective tissue disease.

CD4+ (helper/inducer) T lymphocyte subsets were studied in the peripheral blood from patients with mixed connective tissue disease (MCTD) by double-labelling immunofluorescence. The proportion of CD4+CD45RA+ cells was higher (P less than 0.01) when compared with controls, whereas CD4+CD29+ cells were markedly diminished (P less than 0.001). CD4+CD29+ cells were lower than in patients with progressive systemic sclerosis who were studied in parallel. Upon stimulation with phytohaemagglutinin, CD4+ cells from MCTD patients showed a strong reactivity to acquire the CD29+ phenotype. Expression of high levels of CD29 and other adhesion molecules might lead to facilitated localization of CD4+ cells to inflamed tissue. It is suggested that an increased responsiveness of CD4+ cells to activation signals in vivo and accumulation of CD4+CD29+ cells at tissue sites could result in depletion of this cell subset in the peripheral blood of patients with MCTD.