Developmental profiles of urinary SIgA in newborns and the effect of blood transfusion.

Urinary levels of secretory immunoglobulin A (SIgA) and serum levels of IgA were determined in mature and premature newborns with sensitive enzyme immunoassay methods. On the first or second day following birth, SIgA (3-7 ng/ml) was detected in the urine of both mature and premature babies and the levels tended to decrease for a few days. Beginning with the seventh day after birth, a sharp increase in the urinary levels of SIgA was found in both groups of babies, and at 2 weeks their urine contained about 100 ng/ml of SIgA. A similar developmental profile was seen in serum IgA levels. Upon blood transfusion urinary SIgA levels increased within a day but then gradually fell to normal. A similar change in serum IgA levels was seen in the same patient. A patient who received a massive blood transfusion showed markedly high levels of urinary SIgA.