FIG. 1.

Effects of agonists on adherence and internalization of M1⁺ and M1⁻ streptococci. M1⁺ and M1⁻ bacteria were suspended in RPMI 1640 medium (None), or in RPMI 1640 medium containing the indicated agonist, just prior to infection of monolayers. (a) Intracellular invasion. Percent invasion was calculated as (internalized CFU/CFU in the inoculum) × 100. (b) Streptococcal adherence to A549 cells. Percent adherence is expressed as the percentage of total CFU that remained associated with monolayers after three successive washings with buffer. Data are the means ± standard errors of the means from six to nine infected monolayers (two or three experiments, each performed in triplicate).