Figure 3.

(A,B) Frozen sections of human fetal intestine of 22 weeks of gestation. (A) Is stained with CD3 (T cells in brown) and CD20 (B cells in blue). (B) Is stained for CD3 (T cells in brown) and CD5 (B cells in blue since human fetal B cells are CD5+). Follicles in clusters in (A) or as ILF in (B) are the same in terms of the cellular composition and stage of development. Paraffin sections of human intestine at 4 days old stained for cytoplasmic IgM. (C) Illustrates a cluster of follicles in a Peyer’s patch and (D) illustrates a single follicle that could be classified as an ILF. In (C,D), cytoplasmic IgM+ cells can be identified in the germinal center and on the periphery of the follicle and they appear very similar. There was very little IgA apparent in sections of either in stained serial sections. These images demonstrate that in human ileum there is no apparent developmental difference between follicles in clusters and isolated lymphoid follicles.