Transcript profile of CD4+ and CD8+ T cells from the bone marrow of acquired aplastic anemia patients

Immune-mediated destruction of hematopoietic stem and progenitor cells is pathophysiologic in most cases of aplastic anemia (AA). We have successfully determined the gene expression profile of the marrow CD34+ target cells in AA. T cells producing IFN-gamma and TNF-alpha have been implicated in hematopoietic destruction in AA. We sought to characterize T cells as immune mediators using the microarray approach.

We applied Affymetrix GeneChip techniques to determine the detailed profile of mRNA expression of CD4+ and CD8+ cells from the BM of newly diagnosed AA patients and healthy volunteers. For validation, we confirmed our microarray results using quantitative real-time PCR.

Compared to healthy controls, there were 178 and 183 differentially expressed genes in patients' CD4+ cells and CD8+ T cells, respectively; activities of 22 selected genes were confirmed using real-time PCR. Dysregulated genes included those encoding cytokines/chemokines, and involved in transcription regulation, calcium and ion channel formation, and cell adhesion. Unexpected findings were overexpression of toll-like receptor genes in marrow CD4+ cells of patients and of genes for killer-cell immunoglobulin-like receptors (KIR) in AA marrow CD8+ cells.

Our detailed results at the mRNA level provide insights into the mechanism of AA. Both innate and adaptive immune responses of CD4+ and CD8+ T cells appear to be active in immune-mediated marrow destruction. A variety of cytokines and chemokines active in pathophysiologic cells likely play important roles in the recruitment and activation of lymphocytes to cytotoxic effectors for marrow hematopoietic target cells in AA.