An investigation of the plasma protein changes in rabbits infected intradermally with Type I pneumococci has been carried out, utilizing a cationic detergent method of protein fractionation. A consistent pattern of change was observed. There was an increase in the alpha globulins and fibrinogen concentration which reached maximal levels at the height of the infection. Albumin fell to a minimal concentration when the increment of alpha globulins and fibrinogen was greatest. The beta-gamma concentration showed a significant decrease during the most severe phase of the infection but returned to normal several days after spontaneous subsidence of bacteremia.
The magnitude of these plasma protein alterations depended on the severity of the infection and the response of the host. Significantly greater changes were observed in rabbits severely bacteremic than in those with mild bacteremia. Administration of penicillin suppressed the infection and decreased the usual plasma protein alterations. Injection of cortisone prior to the onset of the Type I pneumococcus infection caused an early inhibition of the expected plasma protein changes, but later the protein pattem developed in the same manner as it did in the severely infected animals.