Reduced dietary protein levels decrease interleukin 3 production of murine splenic T lymphocytes

Production of IL2 and IL3 in syngeneic mixed lymphocyte reactions of BALB/c mice are elevated during a period of moderate dietary protein deficiency

The mixed lymphocyte reaction (MLR) is a model of T cell responsiveness to antigenic peptides complexed with major histocompatibility (MHC) proteins on antigen presenting cells (APC). Since dietary protein deficiencies alter T cell development, syngeneic and allogeneic MLR were investigated in mice fed a low protein 4% casein (4Ca) or control 20% casein (20Ca) diet. Proliferation of splenic lymphocyte populations from BALB/c mice fed 4Ca was increased during syngeneic and allogeneic MLR compared with lymphocytes from mice fed 20Ca. Increased proliferation was accompanied by significantly higher production of IL2 and IL3 during syngeneic, but not allogeneic MLR. To determine the influence of autologous B cells on IL2 and IL3 production during MLR, lymphocyte populations of mice fed 4Ca or 20Ca were depleted of B cells. Splenic lymphocyte populations of mice fed 4Ca that were depleted of B cells did not exhibit increased IL2 or IL3 production during syngeneic or allogeneic MLR. Splenic APc of mice given 4Ca caused greater proliferation during MLR. However, APC of 4Ca mice did not cause greater IL2 or IL3 production. Similarly neither IgM-B cells nor macrophage from mice fed 4Ca induced elevated IL2 or IL3 production during syngeneic or allogeneic MLR. A dichotomy appeared in that 4Ca-APC were able to induce higher T cell proliferation but not cytokine production compared with 20Ca-APC. The enhancement of T cell responsiveness to Class II MHC determinants on APC during moderate protein deficiency appears to require both T and B cells from mice fed the deficient diet.

Protein starvation impairs the ability of activated lymphocytes to produce interferon-gamma

The impairment of lymphocyte function in nutritionally deprived rats was studied. Lymphocytes from rats fed a diet lacking protein showed a severe decrease in their ability to proliferate when stimulated with mitogens. This was accompanied by a dramatic inhibition of interferon-gamma (IFN-gamma) production and a lesser decrease in the release of interleukin-2 (IL-2). Analysis of RNA levels by Northern blot hybridization confirmed that lymphocytes from protein-starved rats had lower levels of mRNAs for IFN-gamma, IL-2, and IL-2 receptor than those from control animals. Protein deprivation therefore leads to a modification of lymphocyte function such that IFN-gamma production in particular is severely impaired.