T-CELL SUBSETS AND T-CELL FUNCTION IN CARTILAGE-HAIR HYPOPLASIA

Cartilage hair hypoplasia is a rare autosomal recessive form of short- limbed dwarfism associated with a cellular immunodeficiency. In eight patients. the authors studied the presence of T cell subsets and in vi tro T cell function in order to address the basis for the immunologica l disorder. Both the proliferative response to phytohaemagglutinin (PH A) and the PHA-induced IL2 production were 60% lower compared with con trols (P = 0.007 and 0.005, respectively). The impaired proliferative response could not be restored by addition of IL-2. This result is in accordance with a decrease in the percentage of activated T cells expr essing the p 55 subunit of the IL-2 receptor complex (CD25). The resul ts define more precisely that T cells from cartilage hair hypoplasia p atients are defective in the transition from the G(0) to the G(1) phas e of the cell cycle. Furthermore, the data demonstrate that several CH H patients show a reduced proportion of CD45RA(+) 'naive' T cells. How ever, the in vitro impairment of T cell function cannot solely be expl ained by imbalance between 'naive' and 'memory' T cells. Although CHH patients with a history of recurrent respiratory tract infections show ed the most aberrant in vitro immune parameters, a clear relationship between clinical data and in vitro parameters could not be established for the whole patient group.