Glossary

ANTIGENS
Foreign molecular structures, which are recognized and specifically bound by components of the immune system (e.g. by immunoglobulins or T cells). The specific binding further promotes immune response reactions.

ANTI-INFLAMMATORY (ANTI-INFLAMMATION)
Anti-inflammation refers to processes that inhibit an immune reaction or inflammation.

B CELLS
See lymphocytes.

COMPLEMENT SYSTEM
A system of interacting plasma proteins (complement factors) that have a bacteriolytic and opsonising effect on the surface of pathogens. They also act as messengers to mediate inflammatory responses. Complement factors are an important component of the non-specific immune system, while they also play a role in the specific defense against pathogens.

CYTOKINES
Small proteins produced and released by cells (mostly immune cells) which act as signaling molecules that have a specific effect on the interaction and communication between cells – e.g. to contribute to the regulation of immune reactions. An excessive release of pro-inflammatory cytokines can cause a so-called cytokine storm, that leads to a hyperinflammatory state.

GRANULOCYTES
Granulocytes are the largest subgroup of white blood cells (leukocytes), accounting for around 50 to 70%. They are part of the innate immune defense, and their main function is the non-specific defense against pathogens. Morphologically and according to the staining behavior of the protoplasm, neutrophil, basophil and eosinophil granulocytes are differentiated.

HYPERINFLAMMATION
An excessive and uncontrolled immune reaction triggered by a severe bacterial infection. Hyperinflammation is also defined as a form of very severe inflammation caused by a cytokine storm (see cytokines).

IMMUNE HOMEOSTASIS
Immune homeostasis is a condition that maintains the balance between immunogenicity to pathogens and the body’s own immune tolerance. It describes the physiological equilibrium of pro- and anti-inflammatory processes in healthy humans.

IMMUNE SYSTEM
The immune system is a highly coordinated defense system of biological organisms that operates in concert to protect the body from pathogens. The complexity of the immune system increases with the phylogenetic developmental stage of an organism. In humans, the immune system consists of involved organs, immune cells and specialized proteins such as immunoglobulins or complement factors.

IMMUNOGLOBULIN A (IgA)
The IgA antibody makes up about 15% of the human immunoglobulins. IgA is the predominant immunoglobulin class in the mucosa and is present as dimer or monomer.

IMMUNOGLOBULIN G (IgG)
Approximately 75% of the immunoglobulins circulating in the blood are of the IgG type, making this immunoglobulin class by far the most common in humans. IgG is the main antibody to trigger antigen-specific secondary immune response reactions.

IMMUNOGLOBULIN M (IgM)
IgM antibodies make up around 10% of the immunoglobulins in human serum. As the largest immunoglobulin, IgM has a pentameric structure consisting of five immunoglobulin subunits, but it can also be present as a hexamer. IgM is the first antibody to be produced and released by the immune system after contact with a pathogen. Accordingly, IgM immunoglobulins are also referred to as the first line of defense against pathogens.

IMMUNOSUPPRESSION
Immunosuppression is a reduction of the activation or efficacy of the immune system. It refers to the entirety of physiological and external processes, e.g. through medication, to suppress immune reactions.

INFLAMMATION
Inflammation is the local and systemic reaction of a biological system to an internal or external stimulus that jeopardizes physiological processes. The aim of inflammation is to eliminate the damaging stimulus and create the conditions for repair processes („healing“). Inflammation is therefore an expression of an organism’s immune response.

IVIG (INTRAVENOUS IMMUNOGLOBULINS)
Intravenously administered immunoglobulin preparations used for therapeutic treatment, which mainly consist of IgG.

LYMPHOCYTES (B AND T CELLS)
Lymphocytes are cells of the adaptive immune system. Lymphocytes make up approx. 25 to 40% of all leukocytes. Three types of lymphocytes are distinguished according to their morphology and function as well as their site of formation and maturation: B lymphocytes, T lymphocytes and natural killer cells (NK cells).

MACROPHAGES
Macrophages are a part of the innate immune response and an essential component of the non-specific defense against pathogens. The phylogenetically oldest immune cells develop from the peripheral monocytes circulating in the blood. Their main function is the phagocytosis of pathogens, foreign substances and dead body cells. After successful phagocytosis, macrophages present antigens to activate the specific immune system.

OPSONIZATION
The mechanism by which pathogens or virus-infected and malignant body cells are marked by antibodies and complement factors. Opsonization enables the immune system to recognize and subsequently eliminate foreign structures, primarily through phagocytic cells.

ORGAN DYSFUNCTION
Condition where an organ does not perform its expected function, which can end up in an organ failure.

PHAGOCYTOSIS
Phagocytosis is a form of cellular endocytosis and refers to the active uptake of larger particles by specialized cells (phagocytes). In addition to the uptake of macromolecular substances, this includes the uptake of pathogens or cellular debris of apoptotic cells. In immunology, phagocytosis is a crucial process that initiates the decomposition of pathogens and the digestion and presentation of antigens by phagocytes.

PLASMA CELLS
Activated and differentiated form of B cells. The function of plasma cells is the production and secretion of antigen-specific immunoglobulins.

PRO-INFLAMMATORY (PRO-INFLAMMATION)
Pro-inflammation refers to pro-inflammatory processes that promote an immune response against a pathogen or an inflammation.

SECONDARY ANTIBODY DEFICIENCY SYNDROME
An acquired antibody deficiency can occur when diseases disrupt the ability of immune cells to react to pathogens and produce antibodies. This form of antibody deficiency can be found e.g. in cancer or autoimmune diseases, in which the underlying disease itself or a necessary immunosuppressive therapy impairs the immune system’s function in the long term.

SEPSIS
Sepsis is defined as a life-threatening organ dysfunction caused by dysregulated host responses to infection.

SEPTIC SHOCK
A critical and life-threatening condition resulting from a severe bacterial infection and organ dysfunction. Septic shock is the final stage of sepsis and is characterized, among other things, by severe vasodilation and an extreme drop in blood pressure. According to Singer et al. (2016), septic shock should be defined as a subset of sepsis in which particularly profound circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone.

T cells
See lymphocytes.