Mast cell responses in mesenteric lymph nodes to infection of rats with the nematode, Nippostrongylus brasiliensis.

The number of mast cells and their distribution in rat mesentery lymph nodes were assessed after a primary infection and after several successive infections with the nematode, . Following primary infection with , two peaks in total mast cell counts were observed. An initial small increase was restricted to day 5 and to the region of entrance to the lymph node. During the second peak, a marked increase in the number of mast cells occurred after day 15, the majority of cells is migrating through the afferent lymphatics, and then advancing from the cortical to the medullary region. The number of cells found in the hilus always remained low, indicating that mast cells accumulate and degranulate within the lymphoid organ. In rats infected several times with the nematode parasite, mast cell numbers were markedly increased and the distribution pattern was similar to that found on day 21 after a primary infection. The observation that the percentage of cells found in the capsule was rather low in these animals indicates that local proliferation might have contributed to the high mast cell counts.