IgE and IgD in human colostrum and plasma

Using radioimmunoassay techniques, we measured IgE and IgD levels in paired colostrum and plasma samples obtained within 4 days postpartum. In colostrum, IgE was detected in concentrations of 0.5-6 IU/ml in 16 out of 39 samples (41%) and less than 0.5 IU/ml in the remainder, whereas IgD was detected in all samples in concentrations of 2-2000 micrograms/dl. Only a moderate correlation was found between colostral and plasma levels of both IgE (r = +0.60) and IgD (r = +0.74). The correlation coefficient between IgE and IgD in plasma was 0.23, whereas in colostrum it was only 0.05. The colostrum:plasma ratio of IgE varied strikingly from that of IgD; the ratio of IgD was 0.1-22.2 times that of IgE. The findings argue against passive transfer of IgE and IgD from the circulation of milk and suggest possible local mammary production of either or both of these two immunoglobulins.