INTERLEUKIN-5 EXPRESSING ALLERGEN-SPECIFIC T-LYMPHOCYTES IN PATIENTS WITH HOUSE-DUST MITE SENSITIZATION - ANALYSIS AT A CLONAL LEVEL

Interleukin 5 (IL-5) is a T-ceIl lymphokine known to stimulate develop ment, functional activity, and in vitro survival of eosinophils. Tissu e and blood eosinophilia occurring during allergic responses of the im mune system are potentially mediated by IL-5 secreting T-cells. To tes t this hypothesis a series of allergen-specific T-cell clones were est ablished from peripheral blood and skin lymphocytes of patients with a topic dermatitis and house dust mite sensitization. In addition, allor eactive T-cell clones were also prepared from peripheral blood lymphoc ytes of healthy donors. Cloned T-cells were analyzed for IL-5 mRNA exp ression and IL-5 secretion by means of in vitro gene amplification usi ng the reverse transcriptase polymerase chain reaction and IL-5 specif ic oligonucleotide hybridization, as well as IL-5-specific ELISA. A ma jority of allergen-specific long-term cultured T-cell clones (84%) of different donors and of either phenotype (CD8+ or CD4+) disclosed IL-5 transcripts on stimulation with lectins. Almost all clones exhibiting IL-5 transcripts also released immunoreactive IL-5 protein into their culture supernatants. In contrast, only 2% of alloreactive T-cell clo nes obtained from healthy donors and none of alloreactive T-cell clone s of one atopic patient investigated expressed detectable amounts of I L-5 mRNA in response to lectin stimulation, all of whom were CD4(+). T hese results suggest that eosinophilia observed in allergic responses in the peripheral blood and in tissues at the site of induced late-pha se cutaneous reaction may be associated with IL-5 release by allergen- specific T-cells.