[Oral challenge with cow's milk in patients with IgA nephropathy--estimation of serum antibodies to cow's milk protein].

The author investigated the serum levels of antibodies against casein, beta-lactoglobulin and lactalbumin before and after challenging with cow's milk in 35 patients with IgA nephropathy, 18 with primary glomerulonephritis except for IgA nephropathy (GN control) and 11 healthy volunteers (H control). Blood samples were obtained at fasting, and at 30, 60, 120 and 180 min after oral challenging with 400 ml of cow's milk. IgA and IgG anti-cow's milk proteins antibodies were analyzed by ELISA. The same challenge was tested after administration of the antiallergic agent, sodium cromoglycate (SCG), in 11 patients with IgA nephropathy and 4 H controls. Serum levels of IgA anti-casein, -beta-lactoglobulin and lactalbumin antibodies in patients with IgA nephropathy were significantly higher than in control groups before challenging. However, those of IgG antibodies were not. The percent change of antibody titer after challenging with cow's milk did not elevate in any group, except for the level of IgA anti-beta-lactoglobulin antibody at 60 min in IgA nephropathy. Cases in which challenging produced marked elevation above the M + 2SD of the levels found in H control were expressed as "positive". The number of "positive" cases was 16 (45.7%) with IgA nephropathy, but none with GN control. There was no significant correlations between "positive" and "negative" cases with IgA nephropathy in clinical manifestations. In 3 out of 4 "positive" patients with IgA nephropathy, the levels of IgA antibody were suppressed after administration of SCG. It is concluded that the serum levels of IgA antibodies against cow's milk proteins are significantly elevated in IgA nephropathy, and are inhibited in elevation after oral challenge with cow's milk by administration of an antiallergic agent in some patients with IgA nephropathy.