Determination of a new phagocytic index: influence of the bacteria strain and leukocyte species.

A scale of response, called phagocytic index (PI), is established to study the phagocytic function by measure of the Nitrobluetetrazoluim (NBT) reduction. 0 % and 100 % opsonic activity must be evaluated before the determination of PI which is calculated as follows: (Formula: see text) OD 0% vary with leukocyte species and the NBT batches, OD 100 % is depended on bacteria strains and nature of cells. Therefore PI must be performed in a system strictly characterized for bacteria, cells, and batch of NBT used. PI provides a better evaluation of bacterial phagocytosis as shown with antisera from rabbits immunized with Haemophilus influenzae.