Types of Reactivity by Severity
The body's response to a stimulus is evaluated by its quantitative and qualitative adequacy. Four main types are distinguished:
- Normoergy — a quantitatively and qualitatively adequate reaction to an agent.
- Hyperergy — an excessive reaction to a stimulus. A striking example is the development of anaphylactic shock upon re-exposure of an antigen into the bloodstream.
- Hypoergy — an inadequately weak reaction to exposure. It is frequently observed in various immunodeficiencies, when an ineffective immune response to a foreign antigen is formed.
- Anergy — a complete absence of the body's reaction. This type indicates severe disruption of vital activity (e.g., the absence of a pain response in a comatose patient).
Specificity and Immunogenicity
Depending on the degree of response differentiation, reactivity is divided into two broad groups:
- Specific — occurs in response to a strictly defined antigen. This category includes the classic immune response and allergic reactions.
- Nonspecific — a reaction to diverse factors without strict specificity. The primary mechanism here is the activation of leukocytic phagocytosis. Triggers can include foreign cells, inorganic particles, bacteria, viruses, and parasites.
Additionally, immunogenic reactivity (vital changes driven by antigenic factors) and non-immunogenic reactivity (vital changes driven by agents lacking antigenic properties, such as psychological, physical, chemical, or biological factors) are distinguished.
Physiological and Pathological Reactivity
Reactivity can be either beneficial or destructive:
- Physiological reactivity is always adequate to the nature and intensity of the exposure. It has adaptive significance, meaning it is beneficial to the organism. An example is normal immunity.
- Pathological reactivity is characterized by an inadequate response in terms of severity or nature. It is always accompanied by a decrease in the body's adaptive capabilities.
Separately, individual pathological reactivity is considered — this is an inadequate reaction in specific individuals to factors that cause no response in the majority of people. A classic example is the development of allergic reactions to common household irritants, food products, or pollen.
Role in Pathogenesis and Principles of Therapy
Pathogenesis represents a complex of interrelated processes of damage and adaptation underlying the development and outcomes of diseases. General pathogenesis (studies general patterns and formulates treatment principles) and special pathogenesis (the mechanism of development of a specific nosological form) are distinguished.
Etiology (cause) often operates on the "switch" principle: a pathogenic factor acts as a trigger, initiating the initial link of pathogenesis. Next, a branched chain of cause-and-effect relationships is formed, and the process develops without further needing the presence of the cause.
Understanding reactivity allows for shaping medical tactics:
- Prophylactic measures aim to identify the cause, suppress risk factors, and activate the immunobiological surveillance system (e.g., using immunomodulators).
- Therapeutic measures are applied when the agent is already acting on the body. Their goal is to terminate or reduce the intensity of the agent's action (using antimicrobial agents for infections, arresting bleeding and transfusing blood substitutes for vascular trauma).