Expand the full form of CMI. (Cell mediated immunity/Cellular mediated immunotherapy)

(i) Health is not just the absence of disease but is a state of complete physical, mental, social, and psychological well-being.

(ii) Factors affecting health are genetic disorders, deficiencies born with or inherited from parents, Infections, lifestyle, including food, water, rest, exercise, habits, etc.

(iii) Good health is maintained through balanced diet, personal hygiene and regular exercise.

2. Disease:

(i)When the functioning of one or more organs or systems of the body is adversely affected, characterised by the appearance of various signs and symptoms indicating poor health.

(ii) It is broadly grouped into infectious and non-infectious. Diseases that are easily transmitted from one person to another. E.g AIDS. They are caused by pathogens, such as bacteria, virus, fungi, and other parasites.They are also known as contagious or communicable diseases.

(iii) Non-infectious disease: Diseases that cannot be transmitted from one person to another. E.g., cancer. They are also known as non-contagious or non-communicable diseases.

(iv) Disease-causing organisms like bacteria, protozoa and viruses are called pathogens.

3. Infectious Diseases:

(i) Vector-borne diseases like malaria,  caused by Plasmodium falciparum, if not treated, may prove fatal.

(ii) Besides personal cleanliness and hygiene, public health measures like proper waste disposal, decontamination of drinking water, control of vectors like mosquitoes, and immunisation are very helpful in preventing these diseases.

4. Immune System:

Our immune system plays a significant role in preventing diseases when we are exposed to pathogens.

5. Innate and Acquired Immunity:

(i) The innate defenses of our body, like skin, mucous membranes, antimicrobial substances present in our tears, saliva, and the phagocytic cells, help to block the entry of pathogens into our body.

(ii) If the pathogens succeed in gaining entry to our body, specific antibodies (humoral immune response) and cells(cell-mediated immune response) help to kill the pathogens.

(iii) Acquired immunity can recognize and selectively eliminate specific microorganisms and molecules (i.e., foreign antigens).

(iv) On subsequent exposure to the same pathogen, the immune response is quick and more intense.

(v) This forms the basis of protection afforded by vaccination and immunisation.

6. Lymphoid Organs:

(i) Lymphoid organs are where the origin, maturation, and multiplication of lymphocytes occur.

(ii) The primary lymphoid organs are bone marrow and the thymus gland.

(iii) The secondary lymphoid organs are the spleen, lymph nodes, tonsils, and Preyers' patches of the small intestine.

(iv) The spleen, the largest lymphatic organ in the body, contains lymphocytes and phagocytes, and it acts as a filter of the blood by trapping blood-borne microorganisms.

(v) Lymph nodes help to trap the microorganisms or other antigens that get into the lymph and tissue fluid.

(vi) The B-lymphocytes function in the form of immunity, called antibody-mediated immunity (humoral immunity), while T-lymphocytes function in cell-mediated immunity (cellular immunity).

(vii) Antibodies are protein molecules called immunoglobulins (Ig) which B-lymphocytes produce.

(viii) Colostrum secreted by the mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant.

(ix) Allergy is a non-infectious, unnatural, and unusual reaction to a substance called an allergen which is generally a weak antigen.

(x) Virus-infected cells secrete glycoproteins called interferons which protect non-infected cells in the vicinity from further viral infection.

7. AIDS:

(i) AIDS caused by the Human Immunodeficiency Virus (HIV) is fatal but can be prevented if certain precautions are taken.

(ii) HIV infects the helper T-lymphocyte (TH) that bears the CD4 receptor site.

8. Cancer:

(i) All cancers are characterised by the uncontrolled growth and division of cells.

(ii) malignant tumours grow rapidly, invading and damaging the surrounding tissues.

(iii) The spread of cancerous cells to distant sites is termed metastasis.

(iv) Many cancers are curable if detected early and appropriate therapeutic measures are taken.

9. Alcohol and Drug Abuse:

(i) Of late, drug and alcohol abuse among youth and adolescents is becoming a major cause of concern.

(ii) Because of the addictive nature of alcohol and drugs and their perceived benefits like relief from stress, a person may try taking these in the face of peer pressure, examinations-related and competition-related stresses.

(iii) Education about their harmful effects, counseling, and seeking immediate professional and medical help would relieve the individual from drug addiction.