HEMATOPOIETIC-CELL RESPONSES IN THE BLOOD AND BONE-MARROW OF SHEEP INFECTED WITH THE ABOMASAL NEMATODE TELODORSAGIA-CIRCUMCINCTA

The generation of bone marrow and blood haemopoietic progenitor colony -forming cells (CFCs) in sheep given primary or challenge infections w ith the nematode parasite Telodorsagia circumcincta is described. Ten days after a primary infection, the frequency of early multipotential- CFCs, eosinophil-CFCs, macrophage-CFCs and mast cell or basophil-CFCs was greater than in controls. These frequencies then declined to pre-i nfection levels by day 21. Blood CFCs (mainly macrophage-CFCs and eosi nophil-CFCs) also increased after infection, indicating a migration of CFCs, presumably to the site of infection. Ten days after challenge i nfection there was less marked myelopoiesis than in the primary infect ion on day 10, though both eosinophil-CFCs and mast cell or basophil-C FCs were significantly above control values. Blood CFC output (mainly macrophage-CFCs and eosinophil-CFCs) reached a peak 2-6 days after cha llenge, evidence of rapid recruitment to the site of infection. Telodo rsagia circumcincta infection is therefore associated with an increase in myelopoiesis, particularly for the cell types characteristic of th e local inflammatory response to abomasal nematodes. There was no corr elation between any of the haemopoietic cell responses measured and wo rm burdens in individual animals after either primary or challenge inf ection.