CYTOKINE GENE-EXPRESSION IN MICE UNDERGOING CHRONIC GRAFT-VERSUS-HOSTDISEASE

Chronic graft-versus-host disease (GVHD) can be induced in B6D2F1 mice by injection of parental DBA/2 lymphoid cells. Stimulation of donor T cells by host MHC antigens leads to the stimulation of host B cells. Little is known of the lymphokines produced during such a reaction. Th is study was designed to directly measure the levels of mRNA for inter feron-gamma (IFN-gamma), interleukin 2 (IL-2), IL-4, IL-5, and IL-10, as well as several other genes, using semiquantitative polymerase chai n reaction (PCR). Semiquantitative PCR was reproducible and signals ge nerated were dependent on the amount of specific RNA or cDNA in each r eaction. Early during the progression of GVHD (2 days after the first injection of parental cells) there was little increase in IL-10 mRNA, a slight increase in IL-4 mRNA, and a dramatic increase in IL-2 mRNA. In addition, IL-2 bioactivity was demonstrated in supernatants from GV H splenocytes cultured in vitro for 24 h. Later in the response (I wee k after the second and final injection of parental cells) IL-4 mRNA le vels were elevated as they were earlier while IL- 10 mRNA levels were dramatically increased. IL-2 mRNA levels were no different in mice und ergoing GVHD than in normal mice at this time. IFN-gamma mRNA was dete ctable both early and late, although at similar levels in normal mice and mice undergoing GVHD. At both times examined, IL-4 was below the l imits of detection by bioassay and IFN-gamma, IL-4, IL-5 and IL-10 wer e below the limits of detection by ELISA. Further studies showed that a majority of the IL-4 and IL-10 mRNA found elevated in GVH mice were produced by Thy1.2+ T cells, with small amounts from B220+ B cells. In addition, the detectable IFN-gamma mRNA found in GVH mice at this lat er time also was produced by Thy1.2+ T cells, with small amounts from B220+ B cells.