Dissociation of helper/inducer T-cell functions: immunodeficiency associated with mycobacterial histiocytosis

Mycobacterial histiocytosis is a generally fatal disease characterized by abundant amounts of undigested atypical mycobacteria present within tissue macrophages that diffusely infiltrate the affected lymph nodes. The immune functions of a 22-year-old man with infection due to Mycobacterium avium were investigated. Although the patient had a marked increase in serum immunoglobulin levels and detectable antibodies toward mycobacterial antigens, he had no cellular response to these antigens both in vivo and in vitro. There was an elevated proportion of blood cells with the helper/inducer (T4+) phenotype, but these cells showed a markedly decreased response to several T-cell mitogens, as well as to autologous and allogeneic cells. The patient's lymphocytes produced diminished amounts of immune interferon, and there was no detectable interleukin 2 (IL-2) activity after stimulation with phytohemagglutinin (PHA). The proliferative response of T4+ cells to pokeweed mitogen (PWM), however, was normal; 47% of these cells bore the Tac antigen, and the production of IL-2 using PWM was within the normal range. No phenotypical or functional abnormalities were found in peripheral blood monocytes. These findings suggest a dissociation of helper/inducer T-cell functions with intact B-cell help, but an impaired ability to activate tissue macrophages or to produce immune mediators.