Augmentation by transferrin of IL-2-inducible killer activity and perforin production of human CD8+ T cells

CD8+ T cell activation correlates with disease activity in clinically isolated syndromes and is regulated by interferon-beta treatment

An increased percentage of blood CD8+ T cells from patients with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) was found to express CD26 and CD69. The percentage of CD26 or CD69 positive CD8+ T cells was higher in patients with MRI evidence of disease dissemination in space or with active MRI lesions than in the remaining patients. Treatment of MS with interferon (IFN)-beta resulted in a decrease in the percentage of CD26 and CD71 positive CD8+ T cells and an increase in the percentage of CD8+ T cells that expressed interleukin (IL)-10 and IL-13. CD8+ T cell activation in MS may be linked to disease activity already at disease onset, and is regulated by treatment with IFN-beta.

The major histocompatibility complex-encoded HFE in iron homeostasis and immune function

HFE is a non-classical major histocompatibility complex class I molecule that complexes with a beta2-microglobulin. A functional link between HFE and iron metabolism has been established by the discovery of a physical association between HFE and the transferrin receptor. By inhibiting transferrin receptor internalization, HFE functions as a negative modulator of transferrin receptor function. In addition, HFE appears to be an iron sensor that directly or indirectly communicates the body's iron status to T cells, which then use cytokines as feedback modulators to achieve iron homeostasis. A working model for the feedback regulatory mechanism between iron metabolism and immune function is proposed.

Upregulation of interleukin-10 and inhibition of alloantigen responses by transferrin and transferrin-derived glycans

Previous studies have shown that critically timed administration of transferrin (Tf) facilitates induction of immunologic unresponsiveness. Here, we determined in mixed leukocyte culture (MLC) and in concanavalin A (ConA)-driven cultures the effect of exogenous Tf and Tf-derived glycans (Tf-Gly) on lymphocyte proliferation. In cultures of human blood lymphocytes, Tf inhibited selectively alloantigen-driven proliferation in MLC, but not ConA-stimulated lymphocyte proliferation. Deglycosylation of Tf abrogated the inhibitory effect of Tf on alloantigen-induced lymphocyte proliferation, and, consistent with a role for glycans, an effect qualitatively and quantitatively similar to Tf was exerted by purified Tf-Gly. Glycans isolated from other proteins, for example, immunoglobulin G (IgG) or fibrinogen, failed to inhibit alloantigen-induced proliferation selectively. Rather, they suppressed lymphocyte proliferation in a non-specific manner. Determination of cytokines in MLC supernatant showed a downregulation of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), IL-2, and IL-12 (p40), along with an upregulation of IL-10, a pattern entirely consistent with the observed effects of Tf and Tf-Gly on alloantigen-induced lymphocyte proliferation. The effect of Tf on MLC was directly IL-10-dependent. IL-10 levels were inversely correlated with lymphocyte proliferation and CD86 expression. Neutralization of IL-10 by anti-IL-10 monoclonal antibody (mAb) blocked the effect of Tf. The MLC-modulating effect of Tf (or Tf-Gly) was not dependent upon the Tf receptor CD71 but appeared to be mediated by a Gly-responsive receptor. These data suggest a role of Tf, and, in particular, Tf-Gly, in allo-interactions that is independent from the role of Tf in iron metabolism, and appears to involve co-stimulatory signals.

Anti-transferrin receptor monoclonal antibody: a novel immunosuppressant

BACKGROUND

Transferrin receptor is a widely distributed cell surface receptor present on most proliferating and highly specialized quiescent cells. Expression of transferrin receptor on the surface of immune cells is up-regulated during T-cell activation after the interaction of the antigen-MHC with the T cell receptor. The role of transferrin receptor in T-cell activation has not been well-established. Since transferrin receptor is physically associated with the CD3 zeta-chain, blockade of transferrin receptor has the potential to interfere with the T-cell signals important in transplant rejection.

METHODS

Anti-transferrin receptor monoclonal antibody (mAb) was administered in vivo and in vitro to determine whether this agent was effective in prolonging allograft survival and altering cell-mediated immunity.

RESULTS

Using donor C57BL/6J (H2b) hearts transplanted to CBA/J (H2k) recipients, anti-transferrin receptor mAb at the time of transplantation prolonged cardiac allograft mean survival time to 25.7+/-0.9 days compared with untreated (13.3+/-0.6 days, P < 0.05) or isotype-matched (10.7+/-0.4 days, P < 0.05) controls. Anti-transferrin receptor mAb administered in vivo failed to suppress the subsequent allogeneic responses. However, when added to culture, anti-transferrin receptor mAb suppressed the allogeneic cytotoxic T lymphocyte response by 79-100% but not the mixed lymphocyte response.

CONCLUSIONS

These studies are the first to suggest that transferrin receptor is a potential therapeutic target for clinical transplantation. Future studies will determine the most efficacious dose and time for maximal immunosuppression and the mechanisms responsible for the immunosuppression exhibited by antitransferrin receptor mAb.