Place in the structure of immune system pathologies
The spectrum of immunological disorders is quite wide and is divided into several groups depending on the mechanisms of development and clinical presentation. There are four main categories:
- Immunodeficiencies — conditions characterized by a deficiency of protective functions.
- Allergic diseases and hypersensitivity — an excessive, exaggerated reaction to antigens.
- Autoimmune diseases — pathological aggression of the system against the body's own tissues.
- Diseases with immune inflammation syndrome.
Thus, immunodeficiency represents only one of the variants of malfunction in which the immunity fails to cope with its direct task due to the absence or inoperability of certain elements of protection.
Etiology and basic classification
Globally, all immunodeficiencies are divided into two broad groups, the key difference between which lies in the mechanisms of occurrence. Understanding this difference is critically important for differential diagnosis.
Primary immunodeficiencies (PIDs) have a strictly genetic nature. The mechanism of their development is triggered by mutations in genes, which leads to the formation of defective protein products. As a result, the cascade of immune response reactions is blocked or proceeds incorrectly.
Secondary (acquired) immunodeficiencies arise already in the postnatal period against the background of initially healthy genetics. Their development is provoked by exposure to external factors:
- Infectious agents (herpesviruses and HIV are particularly dangerous).
- Iatrogenic factors (for example, targeted immunosuppressive therapy in the treatment of other diseases).
- Physical exposure (radiation exposure).
- Chemical agents (various toxins and poisons).
Clinical presentation of genetic defects
Patients with primary immunodeficiencies have a specific clinical profile, which is based on a pronounced infectious syndrome. Infections in such patients are extremely severe, frequently recur, and demonstrate resistance to standard conservative therapy.
The most typical nosologies are sepsis, otitis media, pneumonia, and meningitis. In addition, against the background of reduced immune control, concomitant pathologies frequently manifest. These include the development of tumor processes, various allergic reactions, and autopathology (autoimmune disorders).
History of study and management tactics
Active study of primary immunodeficiencies began in the early 1950s. The first described nosology was X-linked agammaglobulinemia (a disease associated with a mutation in the X chromosome). To date, scientists have identified more than 100 different mutations in genes responsible for encoding immune response proteins. The classification of these states is based on the affected link of immunity, as well as on clinical and genetic features.
When PID is suspected, the diagnostic algorithm necessarily includes a careful collection of family history to search for a genetic trace in blood relatives. The combination of burdened heredity and recurrent infections is a direct indication for an in-depth study of the patient's immune status. Therapeutic tactics in such cases involve long courses of antibiotic therapy using the latest generation drugs in order to at least somehow control the infectious process.
Briefly: answers to topical questions
Which links of the immune system can be affected in primary immunodeficiencies?
In primary immunodeficiencies, the links of both specific (adaptive) and nonspecific (innate) immunity can be affected. The following levels of damage are distinguished:
- Humoral link — B-lymphocyte defect (predominantly antibody deficiencies).
- Cellular link — T-lymphocyte defect.
- Combined defect — simultaneous damage to the T- and B-links.
- Innate immunity — defects in phagocytes, the complement system, as well as the receptor apparatus or effector molecules.
Which specific nosological forms belong to primary immunodeficiencies with a humoral link defect?
Primary immunodeficiencies with a predominant humoral link defect (antibody deficiency) include the following nosological forms:
- Agammaglobulinemia — including X-linked agammaglobulinemia (Bruton disease).
- Hypogammaglobulinemia — decreased antibody levels.
- Selective IgG deficiency — impaired switching to IgG synthesis.
- Selective deficiency of IgA, IgE, IgD — isolated impairments in the synthesis of corresponding immunoglobulin classes.
- Common variable immunodeficiency (CVID).
What laboratory diagnostic methods are used for an in-depth study of immune status?
For an in-depth study of immune status, a complex of laboratory methods is used, forming the immunogram. The main methods include:
- Flow cytometry — a key method for the quantitative analysis of lymphocyte subpopulations, cytokine levels, and the functional activity of cells (phagocytosis, NK cell activity).
- Determination of specific immunoglobulin levels — to assess the humoral response.
- TUNEL assay — detection of apoptotic bodies to assess the completion of the immune response.
- Assessment of caspase activity — analysis of cell death processes.
What pathogenetic therapy methods are used in primary immunodeficiencies besides antibiotics?
In addition to antibacterial therapy, the treatment of primary immunodeficiencies employs:
- Replacement immunotherapy with immunoglobulin preparations.
- Bone marrow transplantation — a radical method used as a last resort, including in severe combined immunodeficiency.
- Gene therapy for immunodeficiency conditions as a method of correcting genetic defects.
For quick memorization of the causes of secondary immunodeficiencies, use the rule of the "four I's": Infections (HIV, herpes), Irradiation (radiation), Immunosuppression (iatrogenesis), and Intoxication (poisons).
Class and exam questions
What is the main difference between primary and secondary immunodeficiencies?
Primary immunodeficiencies are always caused by genetic mutations and are inherited. Secondary ones develop after birth under the influence of external factors (viruses, radiation, toxins) in the absence of initial genetic defects.
Which clinical signs indicate the possibility of a primary immunodeficiency?
The main markers are severe infections (meningitis, pneumonia, sepsis) that constantly recur and do not respond to treatment with standard conservative regimens.
What serves as a direct indication for an advanced investigation of immune status?
The presence in a patient of a treatment-resistant infectious syndrome in combination with a burdened family history (the presence of similar problems in blood relatives).
What else to study on this topic
- Detailed classification of primary immunodeficiencies by the affected link of immunity
- Mechanisms of formation of autoimmune diseases against the background of immunodeficiency (autopathology)
- The impact of specific viruses (HIV, herpes) on the development of secondary immunodeficiencies
- Methods and laboratory tests for an in-depth study of immune status
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