human health and disease
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Health, for a long time, was considered as a state of body and mind where there was a balance of certain‘humors’.This is what early Greeks like Hippocrates as well as Indian Ayurveda system of medicine asserted. Itwas thought that persons with ‘blackbile’ belonged to hot personality and would have fevers. This idea wasarrived at by pure reflective thought.The discovery of blood circulation by William Harvey using experimental method and the demonstration ofnormal body temperature in persons with blackbile using thermometer disproved the ‘good humor hypoth-esis’ of health.In later years, biology stated that mind influences, through neural system and endocrine system, our immunesystem and that our immune system maintains our health. Hence, mind and mental state can affect our health.Of course, health is affected by
–(i)genetic disorders – deficiencies with which a child is born and deficiencies/defects which the childinherits from parents from birth;
(ii)infections
(iii)life style including food and water we take, rest and exercise we give to our bodies, habits that we haveorlack etc.
Some terms related to immunity :
(1)Immunity : Resistance of the body against a pathogen or disease.
(2)Antigen or Agglutinogen : Substance which stimulates the production of antibodies.(3)Antibody or Agglutinin : It is a complex glycoprotein secreted by B-lymphocytes in response to an antigen.
(4)Antiserum : Serum of any animal which contains the antibody for a specific antigen is called antiserum.
(5)Venom (poison) : Toxic substances secreted by snake and some insect.(6)Agglutination : Antigen antibody reaction is called agglutination and study of antigen-antibody reaction iscalled serology.
Immunity is of two types:(i) Innate immunity(ii) Acquired immunity.
INNATE IMMUNITY
Innate immunity is non-specific type of defence, that is present at thetime of birth. This is accomplished by providingdifferent types of barriersto the entry of the foreign agents into our body. Innate immunity consistof four types ofbarriers. These are :-
(1)Physical / Anatomical Barrier : It is made up of two parts :-
(i)Skin : Skin on our body is the main barrier which prevents entry of the micro-organisms. Outermostlayer of skin is dead (str. corneum), so the bacteria do not grow or enter into it. pH of skin (3 to 5) destroythe bacteria.(ii)Mucosa : Mucus coating of epithelium lining of the respiratory, gastrointestinal and urogenital tractsalso help in trapping microbes entering our body. Mucosa contain mucosal cells and cilia. Mucosaentraps the micro-organism and cilia propel the microbes.
(2)Physiological Barriers : Some physiological processes of body create adverse environment for growth ofbacteria. Acid in the stomach, saliva in the mouth, tears from eyes–all prevent microbial growth.
(i)Fever : High temperature of body, inhibit the growth of microbes.
(ii)pH of body : Acidic pH of various part of body like oral cavity, stomach and vagina inhibit the growthof microbes.
(iii)Secretions : Secretions of body like eyes, sebum contain lysozyme, this enzyme destroys the mi-crobes.
3)Cellular Barrier :-Polymorpho-nuclear leukocytes (PMNL-neutrophils), monocytes and natural killer cells (type of lymphocytes) inthe blood as well as macrophages in tissues can phagocytose and destroy microbes.
(A)Phagocytic Cells - (e.g. Monocytes, PMNL - neutrophil, Macrophage). In response to pathogenicinfection, the total count of WBC in body increases. Phagocytosis is exhibited by some types of WBC'ssuch WBC's are called phagocytes.Most important phagocytes are macrophages and neutrophils. Monocytes are liberated at the site ofinfection these later converted into macrophages.Macrophages are large irregular shaped cells that engulf microbes, virus, cellular debris etc. inresponse to an infection
.(B)Non-Phagocytic cells :(Eg : Natural Killer Cell)It is a large granular lymphocyte cell. During this process apart from the phagocytes, another type of cellscalled Natural killer cells kill virus infected cells and tumour cells of body by creating perforin lined pores inthe plasma membrane of target cells (i.e. infected cells). Water enters through these pores causing swelling andbursting of the diseased cell
(4)Cytokine Barriers : Virus-infected cells secrete proteins called interferons which protect non-infected cellsfrom further viral infection.Interferon are anti-viral protein made up to 270 amino acids secreated by virus infected cells and stimulatesthe adjacent cells to produce the Translation Inhibiting Protein (T.I.P.)By this mechanism interferon limits the infection of virus.Interferons are species specific i.e. interferons produced by one species can protect only cells of same speciesagainst viral infection.Interferons make cells resistant to viral infection by synthesis of antiviral proteins in that cell.Interferons can be used for prophylaxis and treatment of viral infections.INFs - a= activate immune system and destroy tumor. It has shown some success in causing of regression ofKaposi sarcoma in AIDS patients
ACQUIRED IMMUNITY
Acquired immunity, on the other hand, is pathogen specific. It is characterised by memory. This means thatour body when it encounters a pathogen for the first time produces a response called primary response whichis of low intensity. Subsequent encounter with the same pathogen elicits a highly intensified secondary oranamnestic response. This is ascribed to the fact that our body appears to have memory of the first encounter
Features of Acquired immunity :(i)Specificity : Acquired immunity is specific for specific micro-organisms.(ii)Diversity : This system recognise the vast variety of micro-organisms
iii)Discrimination between self and non-self. It can recognise self (body or tissue) and non self (foreign tissue)and respond according to them.
(iv)Memory : When a pathogen enter inside the body, body takes longer times to recognise and respond to it thisis called primary immune response but the memory of this encounter remain in immune system.When similar pathogen enters second time inside the body, body immune system rapidly recognises the pathogenand responds quickly to it. This is called secondary (Anamnestic) immune response . This is based onmemory of immune system
The primary and secondary immune responses are carried out with the help of two special types of lymphocytespresent in our blood, i.e., B-lymphocytes and T-lymphocytes. The B-lymphocytes produce an army ofproteins in response to pathogens into our blood to fight with them. These proteins are called antibodies.The T-cells themselves do not secrete antibodies but help B cells, to produce them.
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