These immunoglobulins (1g) consist of structurally related proteins, also called gammaglobulins, all of which act as antibodies. These components of the immune system include IgA, IgE, IgG, etc., each of which is itself a "family" of more closely related proteins. In the, newborn, immunoglobulins supply "passive immunity", meaning that the mother's immune response to pathogens, a response developed from her own exposure, is made available to the baby through the colostrum in her milk.

Colostrum provides at least two more benefits to the immune system: "transfer factor" and lactoferrin. Transfer factor (TF) refers to a form of RNA (ribonucleic acid) which "transfers" the coding for cell-mediated immunity, meaning the immunity which depends upon T- cells (T-lymphocytes), as opposed to the immunity based on B-cells, which produce antibodies. Whereas the B-cells are short-lived, the T (thymus-derived) immune cells are involved in immune reactions which can continue for months or even years. Colostrum stimulates cell-mediated immunity.