Fig. 1. Squalene-induced peritoneal exudate cells stained for alpha-naphthyl esterase (ANAE) activity (×600 magnification). The large dark stained cells are macrophage (M). Lymphocytes (L) are slightly stained and neutrophils (N) are more faintly stained.

Fig. 2. Macrophage chemotaxis in response to extracellular products from Steptococcus agalactiae (x) and Streptococcus iniae (■). Each value represents the mean macrophage migration (±S.D.).

Fig. 3. (a) Retention profile (absorbance at 280 nm) of Streptococcus agalactiae ECP from a high-pressure liquid chromatography Shodex^® Protein column in 0.1 M phosphate buffered saline. The bar indicates the S. agalactiae ECP eluted for chemotactic assay. (b) Retention profile (absorbance at 280 nm wavelength) of Streptococcus iniae ECP from a high-pressure liquid chromatography Shodex^® Protein column in 0.1 M phosphate buffered saline. The bar indicates the S. iniae ECP eluted for chemotactic assay. (c) Retention profile (absorbance at 280 nm wavelength) of tryptic soy broth from a high-pressure liquid chromatography Shodex^® Protein column in 0.1 M phosphate buffered saline.

Fig. 4. Macrophage chemotaxis in response to semi-purified extracellular product from Steptococcus agalactiae (x) and Streptococcus iniae (■). Each value represents the mean macrophage migration (±S.D.).

Effect of varying the concentrations of extracellular product (ECP) from Streptococcus agalactiae in both the upper and lower compartments on Nile tilapia macrophages migration to the lower compartment

Mean of duplicate filters, each read in five fields of view using light microscope at 400×. Macrophages added to upper chamber and migration to ECP in lower chamber was measured. Nd indicates not done. Macrophage values without a letter in common are significantly different (P < 0.05).

Effect of varying the concentrations of extracellular product (ECP) from Streptococcus iniae in both the upper and lower compartments on Nile tilapia macrophages migration to the lower compartment

Mean of duplicate filters, each read in five fields of view using light microscope at 400×. Macrophages added to upper chamber and migration to ECP in lower chamber was measured. Nd indicates not done. Macrophage values without a letter in common are significantly different (P < 0.05).