Host immune response to pathogens and predisposition to infections due to autoimmunity.

<p>Antigens from invading pathogens are recognized and presented by innate immune cells (A) such as macrophages and dendritic cells to CD4+ and CD8+ T cells (CTL) (B). CD8+ T cells recognize endogenous antigens presented by MHC class I molecules and exert cytotoxic functions upon activation. CD4+ T cells recognize antigens presented in the context of MHC class II molecules, and under the influence of innate cells and cytokine milieu, CD4+ T cells can be polarized into different subsets such as Th1, Th2, Th17, and regulatory T cells (Tregs) that secrete distinct cytokines. CD4+ T cells provide help to B cells to produce antigen-specific antibodies (C). However, due to autoimmunity, neutralizing autoantibodies can be produced against any of these key components of the immune system critical for mounting anti-microbial responses and might either predispose to an increased risk of bacterial, viral, and opportunistic fungal infections or exacerbate the ongoing infectious diseases. Indeed, in patients with infections, the occurrence of neutralizing autoantibodies against several key cytokines such as IFN-γ, IL-6, GM-CSF, IL-17, and IL-22 (highlighted in red boxes) that interfere with the host immune response to pathogens have been demonstrated. In addition, autoantibodies are also reported against type I IFNs and IL-12 that might play role in predisposition to infections (highlighted in blue boxes). CTLA-4, cytotoxic T lymphocyte antigen-4; CTL, cytotoxic T lymphocyte; FasL, Fas ligand; GM-CSF, granulocyte/macrophage–colony stimulating factor.</p

Characteristics of the study population.

*<p>Two-tailed Mann-Whitney test; † Mean±SEM (range); ND: Not Documented; ^#Fisher's exact test.</p>‡<p>All patients received Steroids, Cyclosporin, Tacrolimus and/or Mycophenolate Mofetil; one patient received both Basiliximab and anti-thymocyte globulins.</p

Treatment with IVIg is associated with a transient decrease in levels of PFR-MCA hydrolyzing IgG.

<p>IgG was purified from the plasma of patients who received IVIg therapy prior to transplantation (full circles) and from patients who did not received IVIg (empty circles). Plasma had been collected prior to renal transplant (D0) and 3 (M3), 12 (M12) and 24 (M24) months after renal transplant. IgG (66.67 nM) was incubated with PFR-MCA (100 µM), a peptide chromogenic substrate, for 24 hr at 37°C. The amount of hydrolysis was quantified by measuring the fluorescence of the leaving MCA moiety, and is expressed in femtomoles of substrate hydrolyzed per minute per picomoles of IgG. Pooled normal human IgG was used as a control source of IgG. Panel A depicts the raw results as scatter dot plots. Panel B depicts the evolution of the mean ± SEM levels of PFR-MCA-hydrolyzing IgG in the two groups of patients with time (*: P = 0.004). The dotted line represents the hydrolysis of PFR-MCA by normal pooled human IgG (mean of 29 measurements; Coefficient of variation: 0.29). Panel C depicts the levels of PFR-MCA-hydrolyzing IgG in patients treated with anti-thymocyte globulins (ATG, full squares) or not (empty squares), as measured in plasma collected 3 months post-transplantation.</p