SELECTIVE ENRICHMENT OF T(H)1 CD45RB(LOW) CD4+ T-CELLS IN AUTOIMMUNE INFILTRATES IN EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS

The cytokine effector status of CD4+ T cells from lymph nodes (LN) and the central nervous system (CNS) of SJL/J mice immunized with autoantigen in adjuvant for the induction of experimental allergic encephalomyelitis (EAE) was compared. CD4+ T cells were FACS sorted based on the levels of expression of the activation marker CD45RB. Low levels of expression of this surface marker are induced by antigen recognition and are associated with 'effector' T cell function. Reverse transcriptase polymerase chain reaction (PCR) was used to analyze the expression of different T cell cytokine genes in the sorted populations. CD45RB(low) cells constituted a minority of CD4+ cells in the LN and expressed elevated levels of IL-2, IFN-gamma, and IL-4 mRNA, whereas the CD45RB(high) CD4+ population did not express detectable message for these cytokines under linear PCR conditions. By contrast to the LN, CD4+ cells from the CNS were predominantly CD45RB(low) and expressed readily detectable levels of IL-2 and IFN-gamma mRNA, but almost no IL-4 transcription could be detected. IL-4 mRNA levels in CNS were 100- to 250-fold lower than in LN. Also, IL-4 message could not be detected in the CNS 1 week after remission. A cytokine-specific immunocytochemical single cell staining technique was used to enumerate cytokine-producing cells in LN cell populations and in CNS infiltrates. Between 1 and 5% cells in isolated LN cells produced detectable IL-2 and IFN-gamma. By contrast, the frequency of cytokine-producing cells stained in perivascular infiltrates in frozen sections from the brains of animals with active EAE was 10-fold higher. The frequency of cytokine-producing cells correlated closely with that of CD45RB(low)-expressing cells in both the LN and the infiltrated brain. Our results confirm the functional significance of the CD45RB phenotype and indicate an enrichment of T(h)1 cells in the CNS, which suggests an active selection process in the activation/accumulation of antigen-specific T cells at the site of inflammation.