Quantitative determination of immunoglobulins, lysozyme, and certain electrolytes in breast milk during the entire period of lactation, during a 24-hour period, and in milk from the individual mammary gland.

During a period commencing at birth and lasting for up to 27 months 193 milk samples have been collected from 29 mothers. The IgA globulin content was high immediately after birth, averaging 2.7 arb.U, decreasing to 0.3 arb.U within the first 2 to 3 weeks after birth, then remaining almost constant for the rest of the lactational period. In the case of IgG globulin, similar results were obtained, but the quantity was much smaller. IgM globulin was demonstrated in small quantities during the first 3 weeks of lactation. The lysozyme content varied considerably during the whole lactational period. Individual variations were found for all the immunoglobulins, while the concentration in the individual woman varied only slightly from day to day following in other respects the pattern described above. In 19 mothers IgA, IgG, IgM, lysozyme and electrolyte content were determined in serum and in milk from the right and the left breast on the same day. No difference in content was found between milk from the left and the right mammary gland. A positive correlation was found between the concentrations of IgA and sodium chloride in milk, between those of IgG in milk and serum, and between those of lysozyme in milk and serum. No variations were registered during the individual breast feeding, nor for the 24-hour period as a whole.