Main Postulates of the Immune Hypothesis
According to this theory, the nervous system's ability to record and reproduce experience bears a deep resemblance to how the organism recognizes foreign agents (antigens) upon repeated contact. This process is based on the principle of genetic predetermination.
The surface membrane of immunocompetent cells (lymphocytes) is genetically equipped from the outset with a full complement of diverse antibodies. These structural molecules act as specialized receptors awaiting an encounter with their corresponding antigens. An important foundational concept here is clonality: all lymphocyte cells possessing absolutely identical protein receptors are grouped into a single specific clone.
Response Dynamics: From Primary Encounter to Memory Cells
An organism's interaction with a novel stimulus triggers a cascade of strictly defined reactions.
- Primary response. The first encounter with an antigen causes active proliferation — a sharp increase in the number of corresponding lymphocytes. At this point, the clone is finally formed and differentiates into two fundamentally different groups of cells:
- Effector cells — their lifespan is strictly limited to just a few days.
- Memory cells — remain circulating in the body throughout its entire life.
- Secondary response. Upon re-exposure to the same antigen, the process proceeds differently. The surviving memory cells possess a unique ability to rapidly transform into newly formed cells of both types, ensuring a fast and efficient reaction.
Application of Immunological Principles to the Nervous System
Projecting the immunological patterns described above directly onto the nervous system makes it possible to explain the neurophysiological fixation of memory traces.
It is hypothesized that during learning and memorization, an enhanced synthesis of specific antigen proteins occurs. These molecules are targeted directly into the perisynaptic space of neurons. It is their presence and accumulation in this critically important zone that serves as the triggering mechanism for processes absolutely analogous to those occurring during immune response formation, ensuring reliable information storage in the brain.
I.P. Ashmarin's Immunochemical Memory Hypothesis
Special attention is warranted for the immunochemical hypothesis proposed by I.P. Ashmarin. It details cellular mechanisms, emphasizing the close interaction of neurons not merely with each other, but with clones of astrocytic glial cells.
The mechanism of memory trace development includes the following stages:
- Primary induction of astrocyte proliferation occurs, followed by their formation of specific antibodies.
- These newly synthesized antibodies specifically and selectively interact with the postsynaptic membranes of precisely those neurons that were involved in the reaction.
- As a result of this protein binding, a marked facilitation of neural conduction occurs in the corresponding synapses.
Just as with lymphocytes of the immune system, an astrocyte clone formed in this manner retains its structure and persists in the nervous tissue throughout the individual's subsequent life, serving as the material substrate of long-term memory.
Briefly: answers to topical questions
What specific antigen proteins are synthesized by neurons during the learning process?
Sources indicate that learning is accompanied by the synthesis of specific polypeptides and brain-specific proteins. When applying the immunological hypothesis to the nervous system, mention is made of the enhanced synthesis of specific antigen proteins entering the perisynaptic space, but the specific names of these exact antigen proteins are not provided.
A number of proteins involved in memory processes have been isolated from the brain:
- Protein S-100 — interacts with the outer and contractile membranes of neurons with the participation of Ca²⁺ ions.
- Protein 14-3-2 — functions as an enzyme.
- Cholinoceptive protein.
- Acetylcholinesterase.
How does Ashmarin's immunochemical hypothesis differ from Hyden's protein theory of memory?
According to sources, the difference between Ashmarin's immunochemical hypothesis and H. Hyden's hypothesis is as follows:
| Criterion | Ashmarin's Immunochemical Hypothesis | H. Hyden's Hypothesis |
|---|---|---|
| Primary mechanism | Interaction of neurons with clones of astrocytic glial cells | Rearrangement of bases in RNA molecules followed by the synthesis of specific proteins on altered RNA templates |
| Key processes | Induction of astrocyte proliferation and antibody formation; specific interaction of antibodies with the postsynaptic membranes of the same neurons | Nerve impulses affect neurons; base rearrangement occurs in RNA; specific proteins are synthesized on altered RNA templates |
| Effect | Facilitation of conduction in corresponding synapses | Specific proteins determine the selective sensitivity of neurons to a specific impulse configuration |
To remember the essence of Ashmarin's hypothesis, use the "Three A's" rule: Ashmarin — Astrocytes — Antibodies. Astrocytes actively proliferate, secrete antibodies that permanently anchor to the neuron's postsynaptic membrane.
Class and exam questions
What types of memory does this theory connect?
The theory links the mechanisms of classical neuronal memory with genetic and immunological memory (the body's ability to unerringly recognize antigens upon repeated contact).
What happens to lymphocytes during a primary response?
Proliferation of corresponding lymphocytes occurs, along with clone formation and their differentiation into short-lived effector cells (living for a few days) and long-lived memory cells (persisting for a lifetime).
What is the main role of astrocytes according to I.P. Ashmarin's hypothesis?
Astrocytes induce their own proliferation and form antibodies. These antibodies specifically bind to the postsynaptic membranes of neurons, leading to sustained facilitation of conduction in the synapses.
What else to study on this topic
- Mechanisms of specific antigen protein synthesis in neurons.
- The role of the perisynaptic space in molecular exchange between neurons and glia.
- Functional differences between effector lymphocytes and memory cells.
- The effect of glial antibodies on the permeability of postsynaptic membranes.
- Features of the formation and maintenance of astrocytic glial clones.
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