Histological structure and lymphoid cell types in the distal colon aggregate of lymphoid nodules of 4-month old and 22-month old rats

This study had two goals (I) to determine the general histological characteristics of the rat distal colonic lymphoid nodules; and (2) to characterise the immunohistochemical localisation of proliferating cells, apoptotic cells, B lymphocytes and cytotoxic T lymphocytes within the colonic lymphoid aggregates in young (i.e., 4-month old and old (i.e., 22-month old) rats. The immunohistochemical staining described in the article revealed the distal aggregates of lymphoid nodules (ALN) of the rat to be quite similar in structure and cell types to previously described intestinal lymphoid aggregates. There were no major differences in the distribution pattern of proliferating cells, apoptotic cells, B cells or cytotoxic T cells between that of the distal lymphoid aggregate and that of small intestinal Peyer's patches or that of the rat proximal colon ALN. With the techniques and markers employed here, no apparent change with age was observed in the distal ALN.