Postnatal development of the splenic white pulp in the golden hamster Mesocricetus auratus. I. The periarterial lymphoid sheath (PALS).

The histological organization of the periarterial lymphoid sheath (PALS) was studied during the postnatal life of the golden hamster Mesocricetus auratus with special interest in the cell components occurring in each of their regions. Our results suggest a role of the cell components defining the splenic microenvironment at each developmental stage in governing the developmental process. This process can be temporarily and histologically divide into three stages: 1. At birth, a few lymphocytes and lymphoblasts surrounding the central artery define primitive PALS. 2. A second period is determined on the 2nd day by the appearance of a marginal sinus which bounds the two splenic compartments, white and red pulp. The PALS increases circumferentially around the central artery defined by the pattern of reticular cells and fibres. 3. Between the 4th and 10th days, the PALS reaches its definitive organization, except for the absence of primary and secondary lymphoid follicles, defining an inner and outer region. The marginal zone appears on the 6th day.