HIV-1-contaminated individuals with low CD4 T cell counts displayed decreased IgG response to most, but not all microbial antigens and increased IgM response to food antigens. microbiota-specific IgA and IgG may be an important factor contributing to the translocation of microbial antigens across the intestinal mucosal barrier and their systemic dissemination that drives chronic inflammation in HIV-1-infected individuals. == Author Summary == Despite significant effort, our understanding of how HIV-1 virus undermines the immune system is limited. HIV-1infection is characterized by extensive damage to intestinal mucosal barrier and translocation of bacteria and microbial products into the systemic circulation. Immune activation induced by microbial products results in chronic inflammation that drives HIV-1 pathogenesis and progression to AIDS despite successful control of HIV-1 replication by antiretroviral therapy. Here we provide evidence indicating that antibody-producing cells in the intestinal mucosa of HIV-1-infected individuals have decreased capacity to switch from the production of IgM to IgA and IgG, the types of antibodies that normally restrict the translocation of bacterial antigens across the mucosal barrier. This may facilitate systemic dissemination of microbial products and subsequent inflammation in HIV-1-infected individuals. Pectolinarigenin Furthermore, the accumulation of IgM in gut mucosa may contribute to the Rabbit Polyclonal to JAK2 (phospho-Tyr570) exacerbation of inflammatory processes by the formation of inflammatory immune complexes. This newly identified dysregulation of immune system alters our understanding of HIV-1 pathogenesis and may facilitate the design of novel therapies targeting immune dysfunction in HIV-1/AIDS. == Introduction == Compartmentalization of systemic and mucosal immunity restricts adaptive immunity to intestinal microbiota by a complex system of physical and bioactive barriers. This compartmentalization is usually altered in conditions associated with increased gut epithelial permeability resulting in systemic immune responses to intestinal microbial antigens [16]. Massive depletion Pectolinarigenin of CD4+T cells in lymphoid tissue, most profoundly in gut-associated lymphoid tissue (GALT), in the first weeks of HIV-1 contamination sets the overall course of the ensuing disease [710]. The extent of this initial hit to the mucosal immune system appears to determine disease progression; in this sense, first battle decides the war [11]. Accumulated evidence demonstrates that HIV-1 and simian immunodeficiency virus (SIV) cause extensive damage to the gastrointestinal mucosal surface, epithelial microenvironment, and antimicrobial functions of the mucosal barrier [8,12,13]. Elevated microbial translocation is usually believed to be the primary mechanism driving Pectolinarigenin chronic inflammation in HIV-1-infected individuals [11]. HIV-1 contamination is characterized by continuous activation, rapid turnover, and activation-induced cell death of CD4+and CD8+T cell populations [11,14]. The degree of immune activation represents an independent and more powerful predictor of disease progression than viral load [15].The destruction of supporting lymphoid tissue and activation-driven exhaustion of CD4+T cell regenerative capability ultimately leads to the collapse of CD4+T cell homeostasis [11,14]. Despite significant effort, the precise mechanism underlying chronic T-cell activation in HIV-1 contamination remains unknown. Accumulated evidence indicates that impairment of mucosal barrier function and resulting translocation of bacterial lipopolysaccharide (LPS) and other microbial antigens to the systemic compartment represents the primary mechanism driving continuous activation of CD4+and CD8+T cells in HIV-1 contamination [16,17]. Supporting this view is the fact that limited translocation of LPS is usually observed in Pectolinarigenin chronically infected sooty mangabeys possibly explaining the low pathogenicity of SIV contamination in its natural host [16]. Experimentally induced immune activation in natural hosts of SIV by administration of LPS results in significant increases in viral replication and CD4+T cell depletion [18]. HIV-1-contamination is usually associated with multiple aberrancies in humoral responses to previously as well as newly encountered antigens [19,20]. It is well established that HIV-1 contamination results in polyclonal B cell activation, hypergammaglobulinemia, reduction of memory B cell frequency, and an increase in the frequency of circulating immature B cells [21,22]. Most of these changes occur concomitantly with the initial depletion of CD4+T cells at mucosal tissues [20,23]. However, relatively little is known regarding the effect of HIV-1 contamination around the function of mucosal B cells. A near complete elimination of memory CD4+T cell population in GALT during the acute stage of HIV-1 contamination results in an absence of important regulatory and effector functions these cells play in the control of immune responses to environmental antigens and commensal bacteria on one side and infecting pathogens around the other [11,24,25,26]. Since CD4+T cells are required for immunoglobulin isotype switching and somatic hypermutation of B cells in mucosal lymphoid tissues, depletion of this vital population is likely to have a profound effect on the hosts ability to react to the changing antigenic variety at mucosal barriers [7,11]. Altered Pectolinarigenin production of mucosal antibodies may interfere with the essential role they play in the regulation of immune responses to common microbial and food antigens [25,26]. Increased translocation of microbial products and whole bacteria is observed in.