| Popis: |
Delayed-type hypersensitivity reactions elicited in the footpad of ovalbumin-sensitized mice after challenge with aggregated ovalbumin on day 4 or 8 of immunization are distinct. The former was characterized by a dense mononuclear infiltrate and, macroscopically, the reaction peaked at 48 hr after antigen challenge; the latter was preceded by immediate-type reactions, reached the maximum at 24 hr and faded drastically later. Histologically, oedema and a mixed granulocytic-lymphocytic infiltrate was found at this time-point. Immunoglobulin G1 (IgG1), IgG2a and IgE antibodies were detected only in plasma obtained after 8 days of immunization. Regarding the cytokines produced by draining lymph node cells after in vitro restimulation, interleukin-4 (IL-4) and IL-10 were predominant after 4 days and interferon-gamma and IL-2 after 8 days of immunization. These two types of delayed-type hypersensitivity (DTH) were used to study the influence of antibody-mediated responses on the inductive and effector phases of cell-mediated immunity. The effector phase of DTH was not affected by immediate-type reactions, as abrogation of these reactions by mediators' antagonists on day 8 or induction of passive reactions by transfer of immune serum on day 4 did not change the extent or kinetics of either type of DTH. Only transfer, before immunization, of whole or T-cell-enriched spleen cells, but not sera, from hyperimmunized donors (high antibody producers) abolished the induction of pure DTH in 4-day immunized recipient mice and changed their cytokine profile to a T helper 2 type. These results indicate that in a non-polarized immune response to a protein antigen there is initially a bias towards cell-mediated immunity, which is gradually dampened by the development of antibody-mediated immunity. |
