S. Asano et al., IMMUNOHISTOLOGIC DETECTION OF THE PRIMARY FOLLICLE (PF) IN HUMAN FETAL AND NEWBORN LYMPH-NODE ANLAGES, Pathology research and practice, 189(8), 1993, pp. 921-927
The primary follicle (PF) emerges as a globular nest of follicular den
dritic cells (FDC) and lymphocytes in the lymph node anlage in the 16t
h gestational week. It increases in size with age but no germinal cent
er is found until several months later, after birth. Using a panel of
monoclonal antibodies, the authors have defined phenotypes of componen
t cells of the PF. The PF contains a B-cell population including IgM+,
CD20+, CD21+, and CD24+ cells, together with a T-cell population incl
uding CD3+, CD4+, CD5+, and CD8+ but no IgG+ cells. It also contains m
any CD5+ B cells and several IgD+ and alkaline phosphatase-positive ce
lls but few CD15+, CD25+, CD30+, CD38+, and Ki-67+ cells. CD24+ and de
ndritic reticulum (DRC)-1+ cells show an irregular meshwork pattern in
the PF. CD5+ B cells appear even before the formation of the PF and i
ncrease after formation of the PF. The lymphocytic phenotype of the PF
is similar to that of the mantle zone of the secondary follicle. The
phenotypic characteristics indicate that the PF appears as an aggregat
ion of CD5+ B cells and plays an important role as the ancestor of the
secondary follicle as well as helper T cells and FDC.