Pneumococci killed by acetic acid at pH 4.2, then allowed to become Gram-negative at pH 7.0, under conditions such that no cellular disintegration takes place, release in solution small amounts of a substance which is precipitable by acetic acid, and soluble at neutral reaction. This soluble fraction injected into rabbits by the intravenous route causes the production of antibodies which afford...

1. A definite degree of active immunity can be induced in mice through the repeated inhalation of live pneumococci. 2. Only slight immunity is induced in mice by the repeated inhalation of killed organisms.

Pseudomonas exotoxin A (PE) is one of the most potent cytotoxic agents produced by Pseudomonas aeruginosa. In this study, we examined the possibility of using PE with a deletion of 38 carboxyl-terminal amino acid residues, designated PE(Delta576-613), for active immunization against PE-mediated disease. We first examined the toxic effects of PE and PE(Delta576-613) on 5- and 9-week-old ICR mice...

Lambs in different stages of development of active immunity against Clostridium perfringens type D were treated with partially purified immunoglobulin in an attempt to superimpose a passive immunity on an existing or developing active immunity. Three different studies were undertaken to determine the impact of partial purified immunoglobulins on these vaccinated animals. In 2 of the 3 studies, ...

BACKGROUND Passively acquired maternal derived immunity (MDI) is a double-edged sword. Maternal derived antibody-mediated immunity (AMI) and cell-mediated immunity (CMI) are critical immediate defenses for the neonate; however, MDI may interfere with the induction of active immunity in the neonate, i.e. passive interference. The effect of antigen-specific MDI on vaccine-induced AMI and CMI resp...

1. Immunization of rabbits with Type III pneumococci is effective in producing active immunity against infection with a virulent strain of the homologous organism. 2. Immunization of rabbits with Type I or II pneumococci, and with R forms derived from any of the fixed types, is equally effective in producing active immunity against Type III infection. 3. Immunization of rabbits with nucleoprote...

1. A combination of poliomyelitis virus and specific human serum is effective for the production of active immunity. 2. For each gram of active virus given intradermally as an emulsion, 6 cc. of human immune serum, injected subcutaneously, was required in our experiments to protect a monkey from paralysis. Some degree of active immunity was induced. 3. Immunity, without symptom of the disease, ...