Immunoglobulin A plays a key role in local immunity preventing microorganism adhesion and its activity. Besides, it participates in virus and antigenes neutralizing. In the blood Immunoglobulin A circulates predominantly as a monomer, and at secretion as dimer in complex with S-component. Transitory decrease of Immunoglobulin A develops in different states: infectious and inflammatory processes, allergies, tumors. Specific disease is selective Immunoglobulin A deficiency which is a primary immunodeficiency. It is considered the most prevalent primary immunodeficiency but its true prevalence is unknown as in most cases it is asymptomatic and is revealed accidentally at laboratory testing. No specific methods of treatment of selective Immunoglobulin A deficiency exist. The literature review contains data on the character of the pathology, clinical presentation and tactics of patient management.

Since the discovery of immunologic tolerance phenomenon, active discussion of the role of genetic and environmental factors in autoimmune disease development has persisted. One of such factors is infections. Microorganisms are considered to be triggers of autoimmune diseases but their role is still not completely understood. Animal experiments conclusively demonstrate how the certain microorganism or its antigen can cause autoimmune pathology. At the same time the results of clinical studies performed on patients with different autoimmune pathologies are hardly decisive and often are contradictory. It should be taken into account that patients with already existing disease were studied in most cases, so interpretation of the data on the association of certain causative pathogens with certain autoimmune pathology should be performed cautiously. The review contains key hypotheses about possible mechanisms of autoimmune reaction development in infections: hypotheses about latent antegens/cryptoantigens, antigen modification, superantigen presence, epitope spectrum extension, molecular mimicry, adjuvant and non-specific effect, antigen complementarity, and idiotypic-antiidiotypic interactions. Their advantages and disadvantages are presented, their comparison is performed. In most cases facts proving one of the hypotheses can be reconsidered in favor of another one. A number of early hypotheses need to be reviewed taking into account modern understanding of innate and adaptive immunity. As more data about relation between infection and autoimmunity is collected, new hypotheses can be developed integrating main claims of previous hypotheses and adding the new ones.

Development and implementation into practice of biologic agents has dramatically changed the approaches to the treatment of many severe diseases. But in the light of experience of their use more and more attention is paid not only to their efficacy but also to side effects. One of such medications is rituximab - a monoclonal chimeric antibody to CD20 antigen, which is expressed on the membrane of pre-B-lymphocytes and mature B-lymphocytes. In the literature more frequently are published the data about late-onset side effects of this medication, particularly hypogammaglobulinemia. The review presents the data on its prevalence after treatment of different diseases with rituximab, its severity, risk of infection. The possible mechanisms of the development of this phenomenon are discussed. Long-term hypogammaglobulinemia was shown to significantly delay the restoration of peripheral compartment of B cells, with over 90% of B cell population presented by naive B cells and significantly decreased concentration of B cells. Literature analysis demonstrates that the risk of hypogammaglobulinemia increases in multiple rituximab courses, preceding immunosuppression, decreased baseline immunoglobulin level. The need for detection of serum level of immunoglobulins before therapy with rituximab is pointed out by many authors, as the main disease can mask primary immunodeficiency, primarily common variable immunodeficiency, which requires life-term replacement therapy with intravenous immunoglobulins. The issue of administration of this therapy in secondary antibodies deficiency is not solved but severe hypogammaglobulinemia or severe infectious and inflammatory processes definitely require it. So to effectively detect hypogammaglobulinemia it is appropriate to perform monitoring of the level of immunoglobulins not only before but also during the treatment with rituximab as well as in several years after its completion.

The review is devoted to the assessment of use of cell adhesion molecules including intercellular adhesion molecule type 1 (ICAM-1) and vascular cell adhesion molecule type 1 (VCAM-1) as additional laboratory markers for severity assessment and as predictors of outcome in septic patients. One of the very important pathogenetic components of this state is known to be endothelium activation replaced by its dysfunction. The level of expression of these molecules on endothelial cell membrane affects leukocyte migration from the vessels to surrounding tissues. Besides, a number of cell adhesion molecules are expressed on immunocompetent cells that influences the development of immune response (both innate and acquired). The main characteristics of ICAM-1 and VCAM-1 are presented, including the possibility of soluble forms formation (sICAM-1, sVCAM-1) due to shedding of cell membrane induced by proteolytic enzymes. The results of literature analysis demonstrate that in sepsis the serum content of sICAM-1 and sVCAM-1 is significantly higher than in healthy subjects. In most cases their level is higher than in patients with other critical states (such as severe infectious inflammatory processes, myocardial infarction, stroke, burns, etc.) that according to some authors allows their using for differential diagnosis of sepsis and other critical states. There is no consensus on correlation with disease severity (sepsis, severe sepsis, septic shock), presence of multiple organ failure and its prediction, and lethal outcomes. Results inconsistency most probably can be explained by differences in study design. Nevertheless, continuing studies in this direction is considered perspective.