Desensitization of delayed-type hypersensitivity by antigen and specific antibody

Desensitization of contact allergy to DNFB in mice. III. Characteristics of immediate desensitization induced by haptenated spleen cells

The immediate effects and mechanisms of desensitization of contact sensitivity to dinitrofluorobenzene (DNFB) were investigated. Intravenous injection of dinitrophenol (DNP)-labeled syngeneic spleen cells caused significant antigen-specific inhibition (greater than 40%) of the contact response within 24 hr in mice that had been sensitized 2 weeks prior to desensitization. With low concentrations of the hapten used for labeling, allogeneic spleen cells were found to be more efficient than syngeneic ones in inducing the down-regulation of the contact response. The most efficient desensitization was produced by DNP-cells that differed from the recipient at the MLS locus. Haptenated spleen cells induced the production of suppressor mechanisms, as spleen cells from animals desensitized with DNP-cells were able to down-regulate recipients in adoptive transfer and could block the passive transfer of contact sensitivity. Procedures that interfere with the development of suppressor cells, e.g., cyclophosphamide and adult thymectomy, interfered with desensitization by DNP-cells. These results are in contrast to desensitization with soluble dinitrobenzenesulfonic acid (DNBS), where suppressor mechanisms have not been shown. The mechanisms for desensitization depend upon the form of the desensitizing antigen.

The immunomodulatory effect of yeast glucan on delayed hypersensitivity

The effect of yeast beta-1, 3-glucan as an immunopotentiator of delayed type-hypersensitivity reactions (DHR) was studied. Delayed-type-hypersensitivity reactions in mice sensitized intraperitoneally (IP) with sheep red blood cells (SRBC) and pretreated three days previously with glucan given IP were significantly increased. However, mice sensitized IP with SRBC three days after the subcutaneous (SC) administration of glucan showed depressed DHR. Glucan given at the same site but not at distance strongly potentiated the DHR induced by SC sensitization with SRBC. Subcutaneous injection of glucan and SRBC given together also resulted in a sustained DHR which persisted twelve days after sensitization when DHR of control mice had waned.

Mechanism of densensitization in DNCB-contact sensitive guinea pigs

Contact sensitivity to dinitrochlorobenzene (DNCB) in guinea pigs could be rapidly suppressed by intravenous injection of dinitrobenzene sulfonic acid sodium salt (DNBSO3). This suppression is transient and antigen-specific. Macrophages from desensitized animals are not inactivated as shown by their ability to react, both in vivo and in vitro to lymphokines produced in a separate system. Therefore, effector lymphocytes are considered the target for the desensitizing antigen. Using an adoptive transfer system it was demonstrated that effector lymphocytes are inactivated by a direct effect of the hapten. Since this inactivation can be reversed by trypsin treatment, a receptor blockade of effector lymphocytes is proposed as the mechanism of desensitization of DNCB-contact sensitive guinea pigs. This does not exclude the possibility that additional mechanisms such as suppressor cells, compartmentalization or endogenous proliferation of lymph node lymphocytes may play an additional role.

Regulation of delayed-type hypersensitivity. I. T suppressor cells for delayed-type hypersensitivity to sheep erythrocytes in mice

Mice injected with 1 X 10(8) sheep red blood cells (SRBC) into the footpad showed high levels of delayed-type hypersensitivity (DTH) to SRBC 4-8 days after the injection. In contrast, mice injected intravenously with 1 X 10(9) SRBC were unresponsive to DTH induction through 1 X 10(8) SRBC injected into the footpad. This suppression of DTH was maintained for at least 6 weeks and was transferable spleen, lymph node and thymus cells to normal syngeneic recipients. Bone marrow cells, on the other hand, did not contain the suppressor cells. The suppression of DTH was antigen-specific in that DTH to chicken red blood cells and contact sensitivity to 2,4-dinitrofluorobenzene was not affected. The suppressor cells were theta-positive and Ig-negative. They appeared in the spleen in optimum number 3-4 days after induction. The suppressor cells affected both the induction and manifestation of DTH. The presence of suppressor and effector cells for DTH inducible by different routes of antigenic presentation reflects the dynamic balance in the regulation of DTH.