Leukocyte inhibition factor in delayed-onset food allergy.

To investigate the possiblity of a cellular immune hypersensitivity reaction in patients who developed allergic symptoms 2 or more hours after ingestion of a particular food, two in vitro tests were employed: leukocyte migration inhibition factor (LIF) and lymphoblastogenesis. Of the children and adults with food allergy, 73% (30 of 41) had a positive LIF test with whole cow's milk or its fractions or corn. Of nonallergic or grass-pollen sensitive controls, 15% (four of 26) had positive LIF. Lymphocyte transformation often correlated with LIF results in food-allergic patients but was also positive in 77% of controls (seven of nine). We suggest that many patients with delayed-onset food-induced allergy symptoms may have a cellular immune component to their sensitivity. Serum IgA, where measured, was absent or low in half of these patients.