Question

Colostrum, the first milk secretion of the mammary gland of cow, is rich in immunoglobulin:
A. IgE
B. IgM
C. IgA
D. IgG

Answer 1

Colostrum is the first secretion of the mammary gland after the birth of the offspring. Colostrum is different from the milk secreted in the later stages owing to the presence of antibodies whose function is to provide immunity to the offspring. The antibodies identify and destroy the disease-causing pathogens which can potentially cause infections in the newborn.

Complete step by step answer: The major immunoglobulin present in cow milk is IgG, this antibody provides passive immunity which is capable of protecting the offsprings from diseases. IgG antibodies provide protection against bacterial and viral infections. Considering the other given options:
A. IgE: These kinds of antibodies are produced in the presence of allergens and are responsible for the initiation of any allergic reactions. These are the methods by which the body fights against the presence of any foreign organism in the body. These antibodies are produced in very minute amounts.
B. IgM: It is the largest produced antibody. These are the first kind of immune mediators produced with the exposure to an antigen. It is one of the earliest forming antibodies in a human fetus.
C. IgA: In contrast to bovine milk, IgA is the major antibody present in colostrum secreted by mammary glands of human beings.
Hence, the correct answer is option D.

Note: Various bioactive compounds present in the human colostrum consists of lymphocytes and antibodies such as IgA, IgG and IgM which provides immunity to the newborn. It also contains a number of cytokines such as interleukins, tumour necrosis factor and many other growth factors.