TABLE 1.

Opsonization of M type 2 S. pyogenes by affinity-purified human antibodies against SOF2^a

Expt	Affinity matrix	Inoculum (CFU)	CFU in:		% Killing
			Control buffer	Purified antibodies
1	SOF2ΔFBD	72	51,600	31,200	40
2	SOF2ΔFBD	40	44,800	25,600	43
3	SOF2-H(38-1047)	85	54,720	14,760	73

^aHuman antibodies against SOF2 were purified by SOF affinity chromatography, mixed with the indicated number of CFU of S. pyogenes strain T2MR, and added to human blood as described in Materials and Methods. The number of CFU after 3 h of rotation was determined by plating dilutions of the mixtures. Controls consisted of adding human IgG equivalent to the amount of affinity-purified SOF antibodies except for experiment 1, where Tris-saline buffer was used.