Immunological assay for the diagnosis of coeliac disease: interaction between purified gluten fractions.

Increased leukocyte migration inhibition factor (LIF) production by coeliac patients' lymphocytes is a reliable immunologic test for gluten-sensitive coeliac disease providing the small peptide subfractions of gluten are used as mitogens. To investigate discrepancies in results obtained in various published studies, subfractions (B2 and B3) of crude gluten peptic tryptic digest [Frazer's fraction III (F3)] were used singly and in combination as mitogens in coeliac patients and compared in various doses with F3. There was significant increased production of LIF with B2 or B3 when tested separately as compared to a mixture of B2 +/- B3 or to F3. LIF production with B2 or B3 was 23.7 +/- 6.9%; with B2 + B3, it was 10.65 +/- 14.7% (t = 4.05; P less than 0.0005); and with F3, it was 9.2 +/- 10.2% (t = 5.8; P less than 0.0005). There was no difference in the response between B2 + B3 and F3 (t = 0.4; P = 0.32). Studies of LIF production following stimulation by various doses and combinations of gluten mitogens in the same patient gave the best results with B2 or B3 in 10 microgram doses, with a tendency to less LIF production with higher dosages or combinations of B2 + B3 or F3, even to abolition of LIF production in some coeliac cases. The LIF assay is a reliable immunologic test for gluten sensitivity, providing the B2 or B3 subfractions are used as mitogens.