The Kines And Immunodeficiency

Because IL-2 is a signal-transducing cytokine, it is involved in the growth, differentiation, and activation of a variety of lymphocyte subsets. The functional receptor consists ofa, B, and y subunits. The B and y chains are necessary for signal transduction. In addition, the y chain is essential for the binding of IL-4, IL-7, IL-9, IL-15, and IL-17. Mutations in the y chain cause human X-linked severe combined immunodeficiency (SCID) (Sugamura et al., 1996).

Deficiencies in IL-2 have been reported in patients with partial T-cell deficiencies and SCID. One subject had only an IL-2 deficiency with no changes in numbers of T and B cells. Bone marrow transplants or IL-2 administration has successfully treated the disease.

In antibody deficiencies, cytokines may be absent or produced in excess. Multiple interleukin deficiencies have been reported in cases of X-linked agammaglobulinemia or common variable immunodeficiency. In contrast, excessive production of IL-6 was reported in patients with hyper-IgE syndrome and Castle-man's disease (Stiehm, 1993).

Cytokine receptor defects have been demonstated in select immunodeficiencies. Defects in theIK>I-y receptor were reported in four children with severe atypical mycobacteria (e.g., M. avis) orsalmonella infections. Molecular biology studies showed that these patients had a point mutation (nucleotide 395) in the receptor gene that introduced a stop codon. The mutation resulted in a truncated protein lacking the transmembrane and intracellular domains required for signal transduction. Another patient had a deletion in nucleotide 131 resulting in a frame shift and a premature stop codon at nucleotide 187. This child died as a consequence of immunization with attenuated bacillus Calmette-Guerin tuberculosis organism.

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