Novel insights into class switch recombination

Current concepts of IgE regulation and impact of genetic determinants

Immunoglobulin E (IgE) mediated immune responses seem to be directed against parasites and neoplasms, but are best known for their involvement in allergies. The IgE network is tightly controlled at different levels as outlined in this review. Genetic determinants were suspected to influence IgE regulation and IgE levels considerably for many years. Linkage and candidate gene studies suggested a number of loci and genes to correlate with total serum IgE levels, and recently genome-wide association studies (GWAS) provided the power to identify genetic determinants for total serum IgE levels: 1q23 (FCER1A), 5q31 (RAD50, IL13, IL4), 12q13 (STAT6), 6p21.3 (HLA-DRB1) and 16p12 (IL4R, IL21R). In this review, we analyse the potential role of these GWAS hits in the IgE network and suggest mechanisms of how genes and genetic variants in these loci may influence IgE regulation.

Immunological Basis for IgE Hyper-Production in Enfuvirtide-Treated HIV- Positive Patients

We previously reported that enfuvirtide (ENF) treatment is accompanied by a selective increase of serum IgE. We asked whether ENF had intrinsic capability to direct B-lymphocytes to switch to IgE and/or if it could drive CD4 T cells to a Th2 phenotype. ENF was added in vitro: (a) to B-lymphocytes stimulated with IgE-switch inducing stimuli; (b) to peripheral blood mononuclear cells. Total IgE production by B cells and IL4 and IFN-gamma production by CD4 T lymphocytes were evaluated, respectively. ENF had no measurable effect on the IgE production by B-lymphocytes. In contrast, it sharply increased the IL4 to IFN-gamma (a correlate of the Th2 phenotype) when added in vitro to T cells from healthy donors or from single ENF-treated patients. The hyper-IgE production in ENF-treated patients is associated with the in vitro induction of a type-2 phenotype in CD4 T cells.

Class and subclass selection in parasite-specific antibody responses

Antibodies are characteristically induced in many parasitic infection processes. The class and subclass of the antibody response is instrumental because each isotype has a distinct biological function. It is thus crucially important for an infected individual to mount the most appropriate secondary antibody response--that is the response that has the best chance of clearing the infection and/or controlling disease. This represents a fundamental of vaccine strategies. Immuno-epidemiological surveys and in vitro models of antibody production have helped to understand some of the goals which should be achieved when designing antiparasitic vaccines.