Human milk lymphocytes bearing the gamma/delta T-cell receptor are mostly delta TCS1-positive cells.

Our laboratories previously reported that the proportion of lymphocytes bearing the gamma/delta T-cell receptor (TcR) is twofold greater in human milk lymphocyte suspensions than in autologous and heterologous blood samples. The present investigation shows that gamma/delta colostral T cells preferentially express non-covalently bound gamma/delta chains, whereas only a few display the disulphide-linked form of the TcR. This contrasts with the picture in the blood, where the distribution of these two nonoverlapping subpopulations is proportionally inverse. These findings are further evidence that the colonization of the mammary gland during lactation by immune system cells is the result of a selective homing process.