Pathogenetic mechanisms of lymphocyte lineage disorders
Fluctuations in the number of lymphoid cells are caused by a disruption of the physiological balance between their production, maturation, and destruction. The basis of cellular deficiency (lymphopenia) consists of three leading mechanisms:
- Impaired development of the lymphoid system due to congenital anomalies in the organogenesis of the immune system.
- Suppression of lymphocytopoiesis under the influence of toxic, radiation, or immunosuppressive factors.
- Accelerated elimination and death of circulating or tissue pools of immunocompetent cells.
Relative and absolute lymphocyte changes
In hematological practice, it is customary to differentiate relative and absolute fluctuations in the cell pool:
- Relative disorders develop when the proportions of the leukocyte differential count change. A typical example is acute infectious inflammation, where a massive acceleration of granulopoiesis with a left shift leads to a drop in the percentage of lymphocytes. This variant also accompanies protracted infections.
- Absolute disorders are caused by a direct depletion of the cell pool and accompany severe immunodeficiencies, neoplastic processes, and the action of external damaging factors.
Causes of absolute lymphocyte deficiency
Absolute reduction of the lymphocyte pool is observed in a wide range of congenital and acquired conditions:
- Primary and secondary immunodeficiencies: reticular dysgenesis, Swiss-type agammaglobulinemia, DiGeorge syndrome, thymoma with immunodeficiency, AIDS.
- Neoplastic diseases of hemopoiesis: Hodgkin's lymphoma (often combined with neutrophilic leukocytosis), acute and chronic leukemias, multiple myeloma.
- Exogenous and drug-induced effects: exposure to ionizing radiation (including radiation therapy), glucocorticoid therapy, treatment with cytostatic agents (L-asparaginase), lithium preparations, nicotinic acid, and the use of antilymphocyte serum.
- Somatic pathologies: congestive conditions and severe edema, decompensated liver diseases, intestinal losses in intestinal lymphangiectasia.
Lymphocytes in the formation of granulomatous inflammation
In chronic pathologies, lymphocytic reactions are closely associated with focal proliferation of mononuclear cells and the formation of granulomas. The classification of the granulomatous process is based on several key features:
| Classification criterion | Forms and types of granulomas | Characteristic features and examples |
|---|---|---|
| Etiology and nosology | Specific | Possess a unique cellular pattern: tuberculosis, syphilis, leprosy, rhinoscleroma |
| Nonspecific | Morphology does not allow establishing the etiology: echinococcosis, alveolar echinococcosis, brucellosis, foreign bodies | |
| Pathogenesis | Immune | Depend on T lymphocytes and type 3–4 hypersensitivity (sarcoidosis, specific infections) |
| Non-immune | Form around foreign particles, dust, or tissue parasites | |
| Cellular composition | Morphological variants | Phagocytomas (macrophagic), epithelioid cell, giant cell |
Class and exam questions
What is the pathophysiological difference between immune and non-immune granuloma?
Immune granuloma is initiated by T lymphocytes via type III and IV hypersensitivity reactions in infections or sarcoidosis, whereas non-immune granuloma arises as a phagocytic reaction to the physical presence of foreign bodies, dust, or parasites.
Why can lymphopenia be detected in the presence of marked neutrophilia?
This is an example of a relative shift: with a sharp enhancement of granulocytopoiesis accompanied by the release of immature neutrophil forms, the percentage of lymphocytes in the differential count decreases even when their total count remains normal.
Which medications directly cause iatrogenic depletion of the lymphocyte pool?
Glucocorticosteroids, cytostatics (specifically L-asparaginase), antilymphocyte serum, lithium preparations, and nicotinic acid lead to a marked decrease in cell counts.
What else to study on this topic
- Features of the suppression of lymphocytopoiesis in reticular dysgenesis and DiGeorge syndrome
- Mechanisms of type III and IV hypersensitivity in the genesis of specific infectious granulomas
- Pathophysiology of intestinal loss of immunocompetent cells in lymphangiectasia
- Tissue cytomorphogenesis of epithelioid and giant cell phagocytomas
- Specific morphological features of granulomas in rhinoscleroma and syphilis
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