Stress and Immunological Changes

It is in the Limbic System that the psychic function of evaluating lived situations, facts, and life events begins. This evaluation always depends on various elements, such as prior personality, lived experience, current circumstances, and cultural norms.

Also originating from the Limbic System are the various interactions between the nervous, endocrine, and immune systems, promoting interactions of corticocerebral perceptions with the hypothalamus.

Stress, as we have stated, whether physical, psychological, or social in nature, is a term that encompasses a set of physiological reactions which, when exaggerated in intensity and duration, eventually cause an imbalance in the organism, frequently with damaging effects.

The first observations of emotional Stress were reported in 1943, when an increase in the urinary excretion of Adrenal Gland hormones was confirmed in pilots and flight instructors during simulated flights, and some years prior, these changes had already been suspected in swimming competitors moments before races.

The original concept of Stress was presented earlier (1936) by the Canadian researcher of French origin, Hans Selye, based on experiments where animals were subjected to various aggressive situations (stressful stimuli), and whose organisms always responded in a regular and specific manner.

Selye described the entire occurrence of Stress under the name General Adaptation Syndrome, which comprised three successive phases: alarm, resistance, and exhaustion. After the exhaustion phase, he observed the emergence of some diseases, such as peptic ulcers, hypertension, arthritis, and myocardial lesions.

There is a personal and particular sensitivity (affective) in each of us, constituting a set of mechanisms that the organism employs when reacting to agents particularly considered stressors, characterizing how each person evaluates and deals with these situations. This personal sensitivity to reality explains why we evaluate challenging situations one way or another, facing them or not, and reacting to them in particular and personal ways, thus "allowing" them to have a greater or lesser impact on the organism.

Between 1970 and 1990, laboratory experiments attempting to prove the relationship between the Central Nervous System (CNS) and the Immune System were highly expressive. In these two decades, cellular depopulation of the thymus in rats was observed through the induction of hypothalamic lesions. It was also demonstrated that destructive lesions in the dorsal hypothalamus led to the suppression of antibody responses. All of this suggested that the hypothalamus would be a kind of integration base between the nervous and immune systems in response to Stress (Moreira, Melo Filho, 1992, Khansari, 1990).

From 1990 onwards, it was also observed that changes occurring in the pituitary gland (hypophysis) could also determine immunological modifications, given that the extirpation of this gland or even its pharmacological blockade prevented the immunological response in laboratory animals (Khansari, 1990).

An early alteration observed during Stress is an increase in the levels of corticosteroid hormones (cortisone) secreted by the Adrenal Glands. It appears that these levels are inversely proportional to the efficacy of adaptation mechanisms, that is, in cases with adequate adaptive capacity, cortisone levels are not very high, but in the case of depressed individuals, therefore, with severe adaptive difficulties, these levels are higher.

The Adrenal Gland seems to have a more or less selective performance in Stress. In states of aggression, while the cortex secretes cortisone, the medulla of the gland also participates, releasing noradrenaline (norepinephrine). In stressful situations of tension and anxiety, medullary release prioritizes adrenaline (epinephrine).

Mello Filho reviewed this 1976 experiment, in monkeys subjected to Stress who showed an increase in levels of 17-hydroxycorticosteroids, catecholamines (adrenaline and noradrenaline), Thyroid Stimulating Hormone (TSH), and Growth Hormone (GH), while a decrease in sex hormones was observed, with this situation reversing as the animal recovered.

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