Thymocytes induced by antigen injection into the anterior chamber activate splenic CD8⁺ suppressor cells and enhance the antigen‐induced production of immunoglobulin G1 antibodies

Abstract

SUMMARYInjection of antigen into the ocular anterior chamber (AC) of a mouse eye (an immunologically privileged site) induces the activation of immunoregulatory NK1.1 + , CD4 ) CD8 ) , T-cell receptor (TCR) ab + thymocytes. These thymocytes transfer the suppression of delayed-type hypersensitivity (DTH) when injected into mice sensitized to the same antigen but do not effect the suppression of DTH. On the other hand, the immunized recipients of these transferred thymocytes produce splenic CD8 + T cells that effect the suppression of DTH. However, it is unclear whether the thymocytes transferred from the AC-injected donor differentiate into and/or activate CD8 + T-splenic suppressor cells. We therefore sought to determine the origin of splenic suppressor cells produced in the recipients of immunoregulatory thymocytes transferred from donors that receive an injection of antigen into the AC. CD45.1 + thymocytes from mice that received an AC injection of 2,4,6-trinitrobenzene sulphonic acid (TNP)-bovine serum albumin (BSA) were transferred to congenic CD45.2 + TNP-BSA-immune recipients. Spleen cells from the recipients were then sorted based on anti-CD45.1 or -CD45.2 antibody binding and assayed for suppressor cells. This was done by the injection of separated spleen cells into the footpad of TNP-BSA-immunized mice, concurrent with the induction of footpad swelling (contact sensitivity) of the footpad elicited by an epicutaneous application of picryl chloride. The systemic distribution of antigen after the injection of antigen into the AC was demonstrated by the injection of fluorescein or 125 I-labelled TNP-BSA into the AC. The results demonstrate that (i) splenic CD8 + T-suppressor cells produced in the immunized recipients of immunoregulatory thymocytes are derived from the CD45.2 recipient of the CD45.1 + thymocytes; (ii) the induction of recipient splenic suppressor T cells by the transferred immunoregulatory thymocytes requires that the recipient be immunized to the same antigen as that used to induce immunoregulatory thymocytes; (iii) antigen is introduced to the thymus after an injection of antigen into the AC; (iv) although the transfer of the suppression of DTH by regulatory thymocytes was not dependent on interleukin-4 (IL-4), CD4 + NK1.1 ) regulatory thymocytes from AC-injected donors enhanced the production of immunoglobulin G1 antibodies to TNP-BSA by an IL-4-dependent mechanism. These observations suggest that the adult thymus plays an active role in the induction and maintenance of anterior chamber-associated immune deviation as manifested by the generation of the suppression of cell-mediated immunity to exogenous antigen and the antigen-induced production of IgG1 antibodies.

Mechanisms of Peripheral Tolerance following Intracameral Inoculation Are Independent of IL-13 or STAT6

“…The possibility remains that IL-4 is needed for the humoral response during the ACAID process (26). It is known that there is both an afferent Tr cell and an efferent Tr cell generated following the injection of Ag into the eye (20,27).…”

Immune regulation and the eye

“…A popular posit is that during ACAID induction, the antigen that is injected into the eye is picked up by indigenous F4/80 + cells, carried through the trabecular meshwork into the bloodstream, and after a possible detour into the thymus [24][25][26] the APC associated antigen makes its way into the spleen. Within the spleen the F4/80 + APC interact with T cells, NKT cells and marginal zone B cells to induce antigen-specific Treg cells that limit both local and systemic Th1 and Th2 response ( Figure 2).…”

Anterior Chamber-Associated Immune Deviation (ACAID): An Acute Response to Ocular Insult Protects from Future Immune-Mediated Damage?

“…These authors suggested that the intracameral injection of particulate antigens and/or the size of the needle used for intracameral injections induces a trauma required to induce ACAID. Macrophages and dendriform cells expressing the dendritic cell marker CD11c are resident in the iris, ciliary body and choroid in the anterior segment 8,10,16,17. Antigen injected into the anterior chamber is taken up rapidly by these cells.…”

“…However, the egress of resident iris cells that engulf antigen to the circulation has been questioned 16. Soluble antigen rapidly exits the anterior chamber via the circulation and distributes similarly to intravenous antigen 8. Some of the antigen that exits the eye could be in a tolerogenic form 19.…”