Capsule reaction produced by Fab of MAb F26G3. Left panel, intact MAb F26G3, 100 μg/ml; center panels, Fab fragments of MAb F26G3 at the indicated concentrations; right panel, irrelevant Fab of MAb 471, a MAb that is reactive with the capsular polysaccharide of C. neoformans, 1 mg/ml.