Stronger inflammatory/cytotoxic T-cell response in women identified by microarray analysis

Abstract

Women develop chronic inflammatory autoimmune diseases more often than men. The mechanisms causing the increased susceptibility are incompletely understood. Chronic immune stimulation characterizes many autoimmune disorders. We hypothesized that repeated stimulation may cause a different T-cell response in women than in men. Microarrays were used to compare gene expression in T cells from healthy men and women with and without repeated stimulation. Four days after a single stimulation, only 25% of differentially expressed, gender-biased genes were expressed at higher levels in women. In contrast, after restimulation, 72% were more highly expressed in women. Immune response genes were significantly over-represented among the genes upregulated in women and among the immune response genes, the inflammatory/cytotoxic effector genes interferon-gamma (IFN-gamma), lymphotoxin beta (LTbeta), granzyme A (GZMA), interleukin-12 receptor beta2 (IL12Rbeta2), and granulysin (GNLY) were among those overexpressed to the highest degree. In contrast, IL17A was the only effector gene more highly expressed in men. Estrogen response elements were identified in the promoters of half the overexpressed immune genes in women, and in <10% of the male-biased genes. The differential expression of inflammatory/cytotoxic effector molecules in restimulated female T cells may contribute to the differences in autoimmune diseases between women and men.

FIGURE 1. Expression profile of T cell genes differentially expressed between men and women

Bars shown greater than zero represent the numbers of genes expressed at higher levels in women than men, while the negative values represent the numbers of genes expressed more highly in men. Error bars represent the FDR of 4%.

FIGURE 2. Expression levels of pro-inflammatory transcripts in restimulated T cells from men and women

PBMC from 10 racially matched male-female pairs were stimulated with PHA, cultured 4 days, then restimulated for 6 hours with PMA + ionomycin. CD4+ and CD8+ T cells were isolated and expression levels of (A) LTB, (B) IFNG, (C) IL12RB2, (D) GZMA, (E) GNLY and (F) IL17A were measured by qRT- PCR relative to β-actin. Results are presented as the mean±SEM of the 10 determinations per group. Dark bars represent transcript levels in the women, and light bars transcript levels in the men.

FIGURE 3. LTB, IL12RB2 and IFN-γ protein levels in restimulated T cells from men and women

(A) LTB and (B) IL12RB2 were measured by immunoblotting in the same restimulated CD4+ and CD8+ cells shown in figure 2. Results again are presented as the mean±SEM of the 10 determinations per group. (C) IFN-γ release by similarly restimulated T cells from 4 additional racially matched male-female pairs was measured by ELISA on the days indicated. Results again represent the mean±SEM of the 4 determinations per group.