Postnatal development of mitogen responsiveness of guinea pig lymphocytes

Guinea pigs are believed to be immunologically mature at birth. There is, however, little data available to support this concept. In this study, the postnatal development of the lymphocyte responsiveness to Tand B-cell mitogens in the guinea pig was investigated. The results show that guinea pigs are not immunologically mature at birth as to the mitogenic responses of blood lymphocytes. The constant level of PHA response in the blood is achieved from the age of 1 to 2 months and that of Con A at the age of 3–6 months. Furthermore, the results support the concept that the emigration of thymocytes occurs also during postnatal life. The emigration of PHA-responsive thymic cells seems to precede and be greater than that of Con A-responsive cells. These findings provide important clues for studies on the ontogenetic development of cell-mediated immunity.