FIG. 4.

CXCL10 localizes at spore structures internal to the exosporium. Untreated B. anthracis 7702 spores (0 h of treatment) and CXCL10-treated spores (1 h of treatment) were used for immunogold labeling with silver enhancement as described in Materials and Methods. Untreated spores demonstrated negligible binding of labeling reagents. In spores treated with CXCL10, gold particles were found to be associated with the exosporium (white arrow), spore coat (arrowhead), and spore coat-cortex interface (black arrow). A lower-magnification field allowing the visualization of multiple spores immunolabeled for CXCL10 is included. When chemokine treatment was performed in water, conditions not permissive to germination, CXCL10 was found to localize to similar spore structures including the exosporium (white arrow), spore coat (arrowhead), and spore coat-cortex interface (black arrow). Representative fields from 2 independent experiments are shown at a ×30,000 (or ×15,000) magnification; the scale bar equals 0.5 μm.