Specific inhibition of allogeneic reactions with disodium cromoglycate

Milligram amounts of disodium cromoglycate (DSCG) inhibit allogeneic responses in mixed lymphocyte culture (MLC) reactions, but do not affect cell viability or suppress lymphocyte responses to either phytohemagglutinin (PHA) or pokeweed (PKW) mitogens. Preincubation of lymphocytes with DSCG is without effect, indicating that membrane binding is an unlikely explanation for inhibition. The HLA-DR tissue typing of cells in the presence of optimal MLC-inhibitory doses of DSCG is normal suggesting that MLC-reactive lymphocytes are not denied recognition of these antigens. Timed studies demonstrate that DSCG must be present continuously during the induction period, for removal of DSCG after 16 hr culture restores MLC reactivity and addition of the drug after 48 hr is without effect. Both natural killing (NK) and cell mediated lympholysis (CML) assays proceed normally in the presence of optimal MLC-inhibitory concentrations of DSCG; however, CML reactions are eliminated by the addition of drug during cytotoxic T cell priming. Background CML reactivity also disappears when lymphocytes are continuously cocultured in DSCG, implying that such killing cannot be attributed to NK activity. DSCG is said to inhibit allergic reactions by impeding calcium flux across mast cell membranes, thereby preventing degranulation, but other mechanisms are required to explain the selective effects on in vitro lymphocyte reactivity.