Interferon-gamma preferentially reduces memory/effector CD8 T lymphocytes in healthy subjects

Area of Science:

• Immunology
• Hematology

Background:

• Interferon-gamma (IFN-gamma) is a cytokine with diverse immune functions.
• Its specific effects on leukocyte subsets, particularly naive and memory T cells, require detailed investigation.

Purpose of the Study:

• To assess the impact of recombinant human IFN-gamma (rhIFN-gamma) on leukocyte dynamics in healthy individuals.
• To investigate the influence of IFN-gamma on naive and memory T cell populations.
• To examine the in vitro effects of IFN-gamma on T lymphocyte adhesion molecule expression.

Main Methods:

• A placebo-controlled, within-subject study involving 6 healthy participants.
• Administration of subcutaneous rhIFN-gamma (100 microg/m2) or saline solution.
• Flow cytometry analysis of leukocyte subsets and in vitro assessment of adhesion molecules.

Main Results:

• IFN-gamma caused significant depletion of T lymphocytes, with a more pronounced effect on CD8+ cells compared to CD4+ cells.
• Both naive and memory CD4+ T cells were equally reduced, while CD8+ memory/effector cells decreased preferentially.
• Decreases were observed in B cells, NK cells, and monocytes; granulocyte counts initially rose then fell.
• No significant upregulation of tested adhesion molecules (CD11a, NKI L16, CD11b, LFA-3, VLA-4) was noted in vitro.

Conclusions:

• A single dose of rhIFN-gamma profoundly alters peripheral blood leukocyte subset numbers in healthy subjects.
• The observed effects on leukocyte counts are independent of minor cortisol level increases.
• IFN-gamma's impact on specific T cell subsets suggests complex immunomodulatory mechanisms.