Retention of lymphocytes in the subcapsular sinus of lymph nodes: a physiological event?

This study examined the lymphocyte content of the subcapsular sinus of lymph nodes of diverse anatomical sites, from euthymic and athymic animals of various ages. One unusual feature which prevailed in young euthymic animals consisted of the accumulation of lymphocytes on the outer wall of the subcapsular sinus, following differential patterns with respect to diverse domains or areas of the subcapsular sinus of a node compartment. It is concluded that such an accumulation is due to the retention of lymphocytes on the sinus outer wall. Whether the retention reflects a step in unspecific defence mechanisms, in an immunological reaction pathway, or a transient state of the misfunctioning of lymph-carried cells, is considered. Some findings favor the latter possibility. In this case, retention would be due to a mild form of lymphocyte alteration caused by the emergence of an abnormal milieu in a drained tissue, and conceivably involving mast cell products. Whatever the case, the retention on the outer wall of the subcapsular sinus, instead of on its inner wall, would prevent any hindering of the usual activity of the latter wall.