on the other hand , the sensitivity and specificity of the mc test were affected by the concentration of antigen : at about 10 ( 2 ) color-changing units ( ccu ) of antigen , all strains were equivalently cross-reactive against the seven antisera , but at 10 ( 2 ) to 10 ( 4 ) ccu the individual strain specificity appeared , whereas at about 10 ( 5 ) ccu little or no antibody was detectable by mc .
C0020960
antisera
C0003241
antibody