Detection of Antibody-Producing Cells of Mice Injected with Antigens of Neisseria meningitidis

Cellular Response of the Rabbit Eye to Primary Intravitreal Injection of Neisseria meningitidis

New Zealand White rabbits were injected intravitreally with approximately 2,500 viable or heat-killed meningococci. The rabbits were killed at intervals from 30 min to 14 days after injection. None of the rabbits produced detectable antibodies. Local antibody production by uveal tract, spleen, or preauricular lymph node cells was not demonstrated. Viable organisms were recovered from the vitreous at periods from 30 min to 48 hr after injection. Failure to recover viable organisms could be correlated with the appearance of large numbers of polymorphonuclear neutrophiles (PMN) throughout the vitreous. Animals injected with viable meningococci demonstrated a progressive inflammatory reaction characterized by an early accumulation of PMN in the vitreous, limbus, and conjunctiva. The cellular infiltrate gradually became mononuclear. By the 14th day postinjection only a few residual inflammatory cells remained at the limbus. This extensive cellular response was lacking in recipients of heat-killed organisms. The defense of the rabbit against intraocular introduction of meningococci therefore seems to be predominantly a cellular mechanism.

Response of mice to injection of ribosomal fraction from group B Neisseria meningitidis

Ribosomes of strain NOR-7 of group B Neisseria meningitidis were isolated by a procedure that included treatment of the cells with sodium dodecyl sulfate, disruption in a French pressure cell, and differential centrifugation. These preparations consisted of 66% ribonucleic acid and 24% protein and sedimented as a single component with a constant of approximately 66S. When used in immunodiffusion tests with homologous rabbit antiserum, untreated ribosomes formed two precipitin lines, when treated with ribonuclease three lines, and when Pronase-digested only one distinct line. Qualitatively indistinguishable reactions were obtained with the same antiserum and ribosomes from group A meningococci, but no precipitation occurred with those of Escherichia coli. When injected into mice, group B ribosomes elicited an increase in the number of antibody-producing spleen cells demonstrable by the hemolytic plaque technique using unsensitized sheep erythrocytes. Sensitization of the erythrocytes with increasing amounts of supernatant fluid of meningococcal cultures progressively reduced the number of demonstrable plaque-forming cells. Neuraminidase treatment of the erythrocytes increased immune hemolysis, whereas Pronase digestion reduced it. Injected mice were protected against homologous and heterologous meningococcal challenge. Both hemolysis and protection-inducing activities of the ribosomes were unimpaired by ribonuclease, but were reduced by Pronase. It is concluded that the immunological response elicited by the meningococcal ribosomes does not involve the group-specific carbohydrate antigen. The immunological mechanism by which the mice are protected against meningococcal challenge remains unknown.