Selective deficiency in IL-2 production and refractoriness to extrinsic IL-2 in immunodeficiency with hyper-IgM

Monoallelic expression of the interleukin-2 locus

The lymphokine interleukin-2 (IL-2) is responsible for autocrine cell cycle progression and regulation of immune responses. Uncontrolled secretion of IL-2 results in adverse reactions ranging from anergy, to aberrant T cell activation, to autoimmunity. With the use of fluorescent in situ hybridization and single-cell polymerase chain reaction in cells with different IL-2 alleles, IL-2 expression in mature thymocytes and T cells was found to be tightly controlled by monoallelic expression. Because IL-2 is encoded at a nonimprinted autosomal locus, this result represents an unusual regulatory mode for controlling the precise expression of a single gene.

Defective antigen-induced lymphocyte proliferation in the X-linked hyper-IgM syndrome

We examined T-cell proliferation in five patients with X-linked hyper-IgM syndrome (XHIM), using a panel of antigens and lectins. All patients had impaired antigen-induced proliferation, whereas their lectin responses were normal. Thus, in addition to severely depressed antibody responses, patients with XHIM have a defect in antigen-specific T-cell proliferation, which may explain their susceptibility to pathogens such as Pneumocystis carinii.

Cryptococcal osteomyelitis and cellular immunodeficiency associated with interleukin-2 deficiency

We describe an unusual example of cellular immunodeficiency associated with interleukin-2 deficiency in an otherwise healthy 15-year-old boy who had isolated cryptococcal osteomyelitis of the scapula at 10 years of age. His previous medical history was remarkable only for prolonged, severe varicella infection at 6 years of age. He had persistent moderate lymphopenia, anergy, and absent lymphocyte blastogenic responses to mitogens, antigens, or monoclonal T cell antibodies. Subnormal blastogenic responses were seen after exposure to high concentrations of phorbol esters. Immunoglobulin levels and specific antibodies were normal. The patient has been in good health since treatment of his osteomyelitis. However, his lymphocyte blastogenic responses to mitogens have remained absent during 4 years of observation; investigation of the cause revealed a specific interleukin-2 deficiency resulting from defective generation of interleukin-2 messenger ribonucleic acid. Secretion of interleukin-1 by monocytes was normal, suggesting that the abnormal blastogenic response and interleukin-2 production were due to a problem intrinsic to T lymphocytes. The generation of messenger ribonucleic acid for interleukin-4 was not affected. Interferon-gamma was produced at subnormal levels. The addition of recombinant interleukin-2 restored lymphocyte blastogenic responses and increased the expression of interleukin-2 receptors. The clinical findings and immunologic abnormalities present in this patient differ from other primary and secondary immunodeficiencies associated with interleukin-2 deficiency. Thus our observations in this patient extend the spectrum of immunodeficiencies associated with abnormalities in the production of this important cytokine.