The blood and broncho-alveolar leucocyte (BAL) responses, to a
primary Necator americanus infection, were studied in male BALB/c
and NIH mice. Following percutaneous infection, a significant blood leucocytosis
occurred in both the BALB/c and NIH strains. The peak response occurred,
in both strains, on day 10 p.i. and this was reflected in the eosinophil
response which peaked at the same time-point. The change in blood eosinophil
numbers, as a result of infection, was found to be the greatest recorded
for any cell type. In BALB/c mice, however, infection elicited a significantly
more intense total leucocyte, lymphocyte and eosinophil response than in
NIH mice. In contrast, the BAL response was more intense in the NIH strain.
Peak BAL responses were observed between days 12 and 16 p.i., in both strains,
and the change in broncho-alveolar eosinophil numbers, as a result of infection,
was found to be the greatest recorded for any cell type. The relationship
between the observed leucocyte responses and resistance to the migrating
larvae of a primary infection is discussed.