Cell-mediated immune responsiveness to measles. Its occurrence as a result of naturally acquired or vaccine-induced infection and in infants of immune mothers

Studies of cell-mediated immunity (CMI) to measles were carried out in patients with natural measles infection, in recipients of live measles vaccine, and in umbilical cord blood specimens from infants of mothers who were seropositive for measles. Evidence of CMI to measles was found in 100% of patients with natural infection but in only 62% of vaccine recipients and, interestingly, in 40% of umbilical cord blood specimens. Eight of these infants were subsequently studied at 4 to 5 months of age, at which time evidence of measles CMI was still detectable in three. Sufficient stimulation of cell-mediated immune mechanisms may be a prerequisite for the development of life-long immunity to measles. The effect of congenitally acquired CMI to measles on the outcome of immunization or of exposure to natural measles during the first year of life remains to be determined.

The antibody response to primary and secondary infection with respiratory syncytial virus: kinetics of class-specific responses

Serum antibody responses to primary and secondary infections with respiratory syncytial virus were determined in 67 hospitalized infants. Responses in IgG, IgM, and IgA immunoglobulin fractions were assayed using an indirect immunofluorescent technique. Infection was confirmed by identification of RSV antigen in nasopharyngeal secretions using indirect immunofluorescence, and by recovery of the virus in tissue culture. IgM specific antibody response was commonly observed within a few days of onset of primary infection and persisted from two to ten weeks. Increases in titer of virus-specific IgG and IgA were observed in infants aged 6 months or more at the time of infection than in younger infants. At one year after primary infection, IgA and IgM specific antibody was undetectable, and IgG antibody was absent or present in low titer. Subsequent reinfection result ed in accelerated antibody response in all three classes of serum immunoglobulin. High titers of RSV-specific IgG, IgM, and IgA antibody were detectable at five and seven days after reinfection. These observations may explain the relatively mild nature of clinical illness associated with RSV reinfections in childhood.

The mechanism of ageing of phosphonylated acetylcholinesterase

1. The extent of potential reactivation of organophosphate-inhibited acetylcholinesterase decreases with time, a phenomenon called ageing. Ageing is due to dealkylation of the alkoxyl group of the residue bound to the enzyme. The rate of ageing is proportional to the electron-donating capacity of the alkyl group. 2. The ageing of phosphophonylated cholinesterase cal also be demonstrated using a phrenic nerve-diaphragm preparation. The same relationship between the rate of ageing and the structure of the alkyl group was observed. 3. Ageing occurs much faster in electrically stimulated preparations than in resting preparations. This may be due to production of a more acidic environment for the enzyme at the active centre by the products of hydrolysis of the acetylcholine released by stimulation.