Goat IgG (Fc) [HRP]

The development of anti-drug Abs in response to biological products (BP) is a major drawback in the treatment of patients. Factors related to the patient, the treatment, and the product can influence BP immunogenicity. Among these factors, BP aggregates have been suggested to promote immunogenicity by acting as danger signals recognized by dendritic cells (DC) facilitating the establishment of an anti-BP CD4 T cell-dependent adaptive immune response leading to anti-drug Abs production. To date, little is known on the mechanism supporting the effect of aggregates on DCs and consequently on the T cell response. The aim of this work was to identify key signaling pathways involved in BP aggregate DC activation and T cell response. We generated aggregates by submitting infliximab (IFX), an immunogenic anti-TNF-alpha chimeric Ab, to heat stress. Our results showed that IFX aggregates were able to induce human monocyte-derived DC (moDC) maturation in a concentration-dependent manner. Aggregate-treated moDCs enhanced allogeneic T cell proliferation and IL-5, IL-9, and IL-13 production compared with native Ab-treated moDCs. We then investigated the implication of Fc gamma RIIa and spleen tyrosine kinase (Syk) in DC activation and showed that they were both strongly implicated in moDC maturation induced by IFX aggregates. Indeed, we found that neutralization of Fc gamma RIIa inhibited DC activation, and consequently, Syk inhibition led to a decrease in T cell proliferation and cytokine production in response to IFX aggregates. Taken together, our results bring new insight, to our knowledge, on how protein aggregates could induce DC and T cell activation via the Fc gamma RIIa-Syk signaling pathway.

We aimed at investigating the influence of clomipramine and selegiline administered in vivo in mice on lymphocyte subsets in lymphoid organs and SRBC-induced humoral immune response. Balb/c mice were given 7 or 14 oral doses (1 mg/kg) of selegiline or clomipramine. Lymphocyte B and T subsets and splenic regulatory T cell (Treg) subset were determined in non-immunized mice 24 and 72 h after the last dose of the drugs. Some mice treated with 7 doses were immunized with sheep red blood cells (SRBC) 2 h after the last dose, and their number of antibody forming cells, haemagglutinin titers and splenocyte subsets were determined. An increase in T lymphocytes and a decrease in B cells were visible in peripheral lymphoid organs, especially after 14 doses of selegiline or clomipramine in non-immunized mice, as well as in spleens of SRBC-immunized mice. The most pronounced change was a decrease in CD4(+)/CD8(+) ratio resulting mainly from an increase in CD8(+) subset after seven doses of the drugs in the non-immunized mice. However, it was of a transient nature, as it disappeared after 14 doses of the drugs. The tested drugs only slightly affected thymocyte maturation and did not alter Treg subset. Selegiline and clomipramine transiently stimulated IgG production in SRBC-immunized mice. Both selegiline and clomipramine administered in vivo modulated lymphocyte subsets. This immunomodulatory effect depended on the drug as well as duration of administration.