Propagation of activated T lymphocytes from endomyocardial biopsy samples of cardiac allografts: influence of the addition of recombinant interleukin-4 to the culture environment.

In vivo, activated T cells can be propagated from endomyocardial biopsy (EMB) samples of cardiac allografts in cultures containing recombinant interleukin-2 (rIL-2). However, T cells are sometimes not propagated in such cultures, even when rejection is present, and at other times the yield of lymphocytes is too small to allow further studies of these graft-infiltrating cells. The current study investigated the effects of the addition of recombinant interleukin-4 (rIL-4) to the culture environment. Cultures were performed on 532 consecutive EMB samples from 120 adult and pediatric heart transplant recipients. Each sample was divided into multiple fragments. Half of the fragments were cultured in media containing 30 U/mL of rIL-2 and the remaining half were cultured under identical conditions but with the addition of 200 U/mL of rIL-4. After 14 days, cell counts were performed, the cell phenotypes were assessed by flow cytometry, and donor specificity and cytotoxicity were assessed using the primed lymphocyte test (PLT) and cell-mediated lympholysis (CML) assay, respectively. Lymphocyte growth occurred in 18% of grade 0-1a EMB in the presence of rIL-2 and in 29% of grade 0-1a EMB in the presence of rIL-2/rIL-4 (p = 0.02). For higher-grade EMB (equivalent to grade >or=1b), the proportion of positive cultures (approximately 39%) was similar in both conditions. For positive cultures, there was a 5-fold increase in the number of cells in the rIL-2/4 cultures compared to rIL-2 alone (1.6 x 10(6) versus 3.4 x 10(5)). Flow cytometry revealed an increase in the proportion of CD8+ cells in the rIL-2/4 cultures (42% versus 23%, p = 0.004). Proliferative responses to donor antigens (as assessed by using the PLT) were comparable between the two groups, but donor-specific cell-mediated cytotoxicity was enhanced on addition of rIL-4. Hence, addition of rIL-4 enhances the propagation of donor-specific T cells from heart biopsy samples, especially in the presence of minimal rejection. This will provide a greater quantity of material for further studies of graft-infiltrating cells.