Blood is made up to 55% plasma and 45% blood cells, blood cells consists of red blood cells, white blood cells and platelets
Red bloods cells impart red colour to blood, they are also called erythrocyte. Their red colour is due to hemoglobin. The function of RBC’s is O2 and CO2 transport and maintenance of PH of blood.
White blood cells are the defence cells of blood. They are divided into 1) granulocytes namely – neutrophils, eosinophils & basophils & 2) Agranulocytes – namely- lymphocytes, *monocytes & plasma cells.
Platelets function for clotting mechanism of blood.
*Monocyte converts itself into macrophage cell in tissues.
While living safely, we do have danger from tigers & snakes, but more than that is the danger from bacteria, viruses and other parasites which enter our body through air we breathe or food or water we eat/ drink.
We survive inspite of their invasion which is due to our defence mechanism. This is called Immunity (Immunitus – freedom from)
Immunity is of two types
Innate Immunity :-
- Is available to us all the time
- It is in the form of barriers, phagocytosis, complement system humoral mechanisms, natural killer cells, eosinophils.
1) Skin is a mechanical barrier plus its sabaceous secretion inhibits bacterial growth by fatty acids & low pH.
2) Tears of eyes.
3) saliva of mouth
4) Acid of stomach
5) Mucus & cilia of airways.
All these fluid contains antibacterial chemicals in addition to their mechanical washing out function.
Phagocytosis - Blood cells namely- neutrophil & macrophage have ability to eat the micro- organism. Neutrophils are present in blood & macrophages in tissues. After eating the micro- organisms, they are broken down by proteolytic enzymes.
Complement System -
Consists of about 20 proteins present in blood. These proteins act by several ways. One mechanism is to cover the micro-organism to get attracted by neutrophils or macrophage. Other is release of histamine & other substances to stimulate migration of phagocytes. Third mechanism is to rupture the cell membrane of micro organism.
Humoral Mechanisms -
Is the production of numerous substances namely, c-reactive proteins & Interferons.
After infection there is rise in c-reactive proteins which adhere to surface of micro-organism to activate complement system.
are released by virally infected cells. Lymphocytes infected by viruses release Interferons, which form a protective ring for other lymphocytes and suppress the synthesis of neucleic acids on which the viruses thrive.
Natural killer cells -
Nk cells are large granular lymphocytes which kill virally infected cells and tumor cells. These cells detect their presence, due to presence of a special glycoprotein present –on cell membrane for recognition (of “We are in danger”). In the bargain, the host cell dies, but it limits the viral multiplication. Normal cells are protected from NK Cells, but tumor cells are destroyed by them.
are specially equipped to deal with large parasites. They produce several lethal substances, causing death of parasite.
Thus to conclude, the body has an impressive armamentarium to deal with invasion and a remarkable co-operation between different weapons, e.g. complement facilitates phagocytosis, CRP activates complement, interferons activate NK cells.
Aquired Immunity -
also called as adaptive immunity
is the one which is developed after exposure to micro-organism.
This aquired immunity is required as many micro-organisms have learnt to get away from innate immunity.
The aquired immunity is of two types
1) Humoral or Antibody mediated,
2) Cell mediated. However this bifurcation have many overlapps.
1) Humoral Immunity - is expressed thro’ circulating antibodies which are proteins. Most antibodies are gamma globulins. These antibodies are produced by B-lymphocytes (so named because their early ‘education’ is in the bone marrow)
The molecule, which induces the formation of antibody is called an antigen. Each antigen evokes different antibody production. In case of infectious organism, the antigen can be part of its body or toxins it produces. Most of the antigens are proteins.
The antibodies are called immunoglobulins. Their classification is as follows -
|IgG ||IgA ||IgM||IgD||IgE
|80%|| 13%|| 6%|| 0-1%|| 0.002%
|Major Defence || Present in|| Early || Antigen || For Helminth
|lasting long||Secretions ||immune||recognition||Evoke Allergy
|Duration|| Tears, Saliva|| response|| ||
|Placenta—Baby|| || recognition|| ||
|Milk—Baby|| Gastric Acid.|| || ||
2) Cell mediated immunity - is invoked, when organisms prefer to stay in cells. This is expressed by large lymphocytes called T lymphocytes, (as their early education site is in thymus). These lymphocytes operate by helping phagocytosis and releasing cytotoxic substances.
Structural components involved in aquired immunity are lymphocytes. They all originate from bone marrow from pluripotent-stem cells. These lymphocytes undergo differentiation in Thymus—T cells or bone marrow itself – B cells.
These T and B cells populate in lymphnodes, lymphoid tissue like tonsils, spleen, lymphoid tissue in gut, respiratory tract and other mucosal surfaces.
Functional pathway -
1. When micro-organism enters body it is trapped by lymphoid tissues and generate immune response.
- If the micro – organism invades the tissues or penetrates the tissues, it is trapped by lymph nodes.
- If it reaches blood stream, it is trapped by spleen.
- if it enters thro mucosal surface then the mucosal lymphoid tissue traps it.
2. Phagocytosis of the organism and degrade it.
3. Coat its surface by fragment derived from it.
4. Recognition of these labelled antigens.
5. Production of antibodies by B limphocytes or activated T cell (cytotoxic lymphocytes) lymphokines.
Body can manufacture by B—cells thousands of antibodies by B limphocytes to match each antigen. The antibody-antigen reaction is not a chemical reaction but physical – as precipitation or agglutination.
Body already has large no. of T cells. When infected i.e. invaded by micro—organism, provide protection by cytokines and killer T cells.
Regulation – of immune system is local and general.
1.Local is challenge and response.
2.General is neuroendocrine and genetic.
Challenge is presence of antigen – its number and toxicity. As body eliminates it, the immune response fades. The response is humoral and cell mediated both. To begin with, IgM comes into picture and them IgG.
- Genetic factors do play a role in efficacy of immune system.
- Immune system & neuro-endocrime system interact in many ways. It is the PNEI – axis i.e. Psycho- neuro-endocrino immunity relationship.
The psychological status may suppress the immune response at limbic system e.g. Anxiety & depression increase the suseptibility of infection, so also stress response. This can be via Autonomic nervous system or Hormonal axis, both acting at Hypothalamus.
Hormones which inhibit immune response are Cortisol, Esterogens, Progesterones, Androgens & that which stimulate immunity are Growth Hormone, Thyroxine, Insulin.
Yoga & Immune System
Body elicits stress response by releasing stress hormones. These are ACTH & cortisol by anterior pituitary & adrenal cortex. In addition sympathetic system stimulation leads to release of adrenaline & nor-adrenaline.
Cortisol suppresses the immune system causing
1) lymphocyte reproduction to decrease markedly. The T lymphocytes are especially suppressed, which promote inflammation.
2) Cortisol decreases the migration of white blood cells into inflamed area & phagocytosis of the damaged cells.
3) Cortisol suppreses the inflammatory response of body by stabilising lysosomal membranes (preventing release of inflammatory mediators like histamine, bradykinin, prostaglandins, leukotrines etc.)
Thus long standing stressful – situations may suppress the individual’s immune system, making him / her susceptible for infection.
Yogic pathway, disciplines our behavior, mind & cognitive process for facing stressful situations in a more amicable way. It helps us to increase our tolerance & adaptability. The habit of constant awareness helps us to understand the effects of our emotions, thoughts, attitude & approach on our body functions. This helps us to minimise stress response & let immune system work efficiently.