Aging and immunoglobulin isotype patterns in oral tolerance

In the present review we address oral tolerance as an important biological phenomenon and discuss how it is affected by aging. Other factors such as frequency of feeding and previous digestion of the antigen also seem to influence the establishment of oral tolerance. We also analyze immunoglobulin isotypes of specific antibodies formed by tolerant and immunized animals of different ages submitted to different conditions of oral antigen administration. Isotypic patterns were studied as a parameter for assessing the pathways of B and T cell interactions leading to antibody production.

Influence of age on the induction of oral tolerance in mice and its adoptive transfer by spleen cells

Seven-week old B6D2F1 mice were highly susceptible to the induction of oral tolerance to ovalbumin (Ova), whereas 70-week old mice were totally refractory. Immune responsiveness (secondary antibody formation) to intraperitoneal immunization to Ova was the same in 7-week or 70-week old B6D2F1 mice. In B6D2F1 mice, the adoptive transfer of spleen cells from old donors into young recipients hindered, and, reciprocally, transfer of spleen cells from young donors into old recipients facilitated the induction of oral tolerance. In BALB/c mice, which are refractory to oral tolerance to Ova, the adoptive transfer of spleen cellsfrom neonate or young donors into old recipients failed to modify the lack of susceptibility to the induction of oral tolerance

A toxoid prepared from cholera toxin by iodination

A cholera toxoid was prepared by iodinating purified cholera toxin having an activity of 25 Limit of blueing (Lb) doses/l ug with 0.8 umol of iodine monochloride per mg toxin, and the residual lesion capacity was tested in mice. The Blueing Dose (BD) test was strongly positive for the native toxin, and co0mpletely abolished in the iodinated toxoid when tested at up to 25 times one Lb dose. The dermal microscopic lesions with intradermal doses of 1 ug virulent toxin presented intense leucocyte infiltration, proteinaceous edema and active hypertemia, whereas none of these effects was observed with the same amount of toxoid. To determine antigenicity, two groups of micereceived toxin or toxoid, 8.5 ug adsorbed to aluminum hydroxide, followed by a booster of 17 ug in saline 21 days later. Measurement of antibodies by ELISA at day 28 indicated that the toxoid was 2.5 times more antigenic than the toxin. These data show iodination converts cholera toxin to an effective toxoid