EVALUATION OF THE USEFULNESS OF LYMPHOCYTE-PROLIFERATION ASSAYS IN THE DIAGNOSIS OF ALLERGY TO COWS MILK

Background: The significance of cell-mediated mechanisms in IgE-mediat ed milk allergy (IgE-MA) and in milk-induced enterocolitis syndrome (M E) is controversial, Some investigators have claimed that lymphocyte p roliferation assays are useful in the diagnosis of food hypersensitivi ty, despite the great variability in study designs and results reporte d, This study was undertaken to address many of these variables slid t o determine whether lymphocyte proliferation assays correlate with cli nical diagnoses. Methods: Lymphocyte proliferative responses to milk a ntigen were evaluated in two groups of children, 27 with IgE-MA, and n ine with ME and in 21 pediatric control subjects. IgE-mediated food al lergy was documented by positive double-blind, placebo-controlled food challenges and positive skin prick test results, ME was diagnosed by oral challenge or by a history of repeated episodes of delayed vomitin g (> 2 hours) after ingestion of milk and by negative skin prick test responses. Peripheral blood mononuclear cells were isolated and cultur ed, Cultures stimulated with milk (the food antigen of interest), soy antigen (a nonrelevant food antigen), or tetanus antigen (a positive c ontrol antigen) and unstimulated controls were performed in quadruplic ate, On days 5, 7, and 9, cells were pulsed with tritium-labeled thymi dine and incubated for 4 hours, Results were compared as counts per mi nute (cpm) and as stimulation indices (SIs). Results: Maximal prolifer ation was generally seen on day 7, The median cpm (20,941) and the med ian SI (19.2) in response to milk antigen in the 27 children with IgE- MA were significantly greater than those in the control patients (6969 cpm; SI = 14.2; p = 0.001 and p < 0.05, respectively), However, the r anges mere large and overlapped extensively (IgE-MA, 5616 to 52,053 cp m; controls, 469 to 39,260 cpm), The non-soy-allergic patients with Ig E-MA also had a significantly greater response to soy antigen than did the control subjects when cpm were compared (0.01 < p < 0.05). There were no differences in background or in response to tetanus antigen, T he median response to milk in the patients with ME (11,975 cpm) was si gnificantly greater than that in control subjects (6969 cpm; 0.01 < p < 0.05), when cpm were compared but not when SIs mere compared, There were no significant differences between the patients with IgE-MA and t hose with ME. Conclusion: Overall, these results indicate that lymphoc yte proliferation assays are neither diagnostic nor predictive of clin ical reactivity in individual patients with milk allergy, Lymphocytes of many control patients are highly responsive to milk antigens, and l ymphocytes of many patients with milk allergy are not, Statistically s ignificant differences are only evident when the patients are compared as groups.