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 vitro T cell function in order to address the basis for the immunological disorder. Both the proliferative response to phytohaemagglutinin (PHA) and the PHA-induced IL2 production were 60% lower compared with controls ( 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 expressing the p 55 subunit of the IL-2 receptor complex (CD25). The results define more precisely that T cells from cartilage hair hypoplasia patients are defective in the transition from the G₀ to the G₁ phase of the cell cycle. Furthermore, the data demonstrate that several CHH patients show a reduced proportion of CD45RA⁺'naive' T cells. However, the in vitro impairment of T cell function cannot solely be explained by imbalance between 'naive' and 'memory' T cells. Although CHH patients with a history of recurrent respiratory tract infections showed 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.