Rickettsial hemolysis: adsorption, desorption, readsorption, and hemagglutination

The energy-dependent adsorption of radioiodinated rickettsiae to sheep erythrocytes was demonstrated. The iodination procedure, however, decreased the hemolytic activity of the rickettsiae. No desorption of rickettsiae from isolated rickettsia-erythrocyte complexes (prevented from lysing by NaF) could be measured. On the other hand, rickettsiae desorbed from this complex during or after lysis and readsorbed and lysed other erythrocytes. Thus, the usual hemolytic assay measures multiple rounds of adsorption and lysis. Although lysis of the rickettsia-erythrocyte complex was insensitive to anti-rickettsial rabbit serum, adsorption and readsorption were completely inhibited by such antiserum. Hemagglutination of erythrocytes by rickettsiae was observed (in the presence of NaF to prevent lysis) and was sensitive to the same inhibitors as adsorption.