Some Important Diseases | Science & Technology for UPSC CSE PDF Download

Some Important Diseases

AIDS The disease is caused by a virus called Human T-Cell Lymphotropic Virus-III or HTLV III. The HTLVs are Retroviruses. 

HTLV III critically injuries the immune system by infecting and eventually killing T-Cells. As a result of progressive destruction of its T-Cells, the body is easily ravaged by a number of common infections agents. In many instances, these infections would have caused little injury were there functional T-Cell clones availables. Unable to battle infections in the normal manner victims that develop a‘full blown’ case of AIDS eventually succumb. In AIDS patients the HTLV-III virus has been shown to be present in semen as well as in the blood. Though the virus is believed to be transmitted principally through sexual contact, a number of haemophilics have contracted the disease as a result of receiving transfusions of infected blood. A number of infants have developed AIDS by transplacental transmission from infected mothers. 

Cancer : Cancer is a disease characterised by excessive and abnormal growth of certain cells. In a healthy individual the growth of cell is balanced by the rate of cell loss. Thus when one attains adult age, the size and cellular contents of various body organs remain constant.  The balance between the growth of the cells and the rate of cell loss may be dislocated by certain chemicals, physical stresses and viral agents. As a result, the normal growth of the cells may be transformed into a cancerous one.

The non-regulated growth of the cells that accompanies cellular transformation produces Tumorsor Neoplasms, each tumor being the product of proliferation of a single abnormal cell. Malignant tumor cells are cancer cells that spread to and take up residence in neighbouring tissues—a condition called Metastasis. Benign tumor cell do not spread to distant sites and do not pose so great a threat to life. The initial work on cancer cells was carried out on the ‘Hela’ cells which were originally derived from a cancerous cervical tumor in 1951 and have been cultured since that time.
Hela is an acronym for Henrietta Lacks, the woman from whose cervix the cells were removed.

Some Types of Cancer

Carcinoma: Cancer of epithelial cells of the skin and the lining of the internal organs. Osteoma: Tumours of the bones. Clioma: Tumors of the connective tissues in the brain and central nervous system. Melanoma: Tumors of the pigmented moles found on the skin. Lymphoma: Tumors of lymph glands. Symptoms of Cancer The five danger signals of cancer:  A lump or hard area in the breast A swelling or sore throat. A persistent cough or hoariness. A change in a wart or mole. A persistent change in diet and bowel habits.

Allergy

The immune system responds to a variety of noninfectious foreign materials, including drugs, pollen grains, certain foods, certain liquids or chemicals, plastics etc.  An allergy (altered reaction) is an inappropriate,over reaction of the immune system. Common allergies are hay fever, asthama and eczema. Antibodies trigger the reaction by combining with both the antigen and the surface of ‘mast cells’. Mast cells are non-circulating cells that form part ofconnective tissue to cause the release of large amounts of a particular protein, histamine, into the blood stream. Histamine, a normal initiator of the inflammatory response, stimulates the dilation of arteries and increased permeability of capillaries, sneezing, coughing, itching, difficulty in breathing, and rashes on the body are all symptoms of an allergy response in a particular region of the body. One method of treating allergies is by drugs, called anti-histamine drugs.

Rejection of transplanted Organ

Sometimes within minutes or hours the recipient rejects the transplanted organ or tissue. This is due to circulating antibodies of the recipient which form complexes with donor tissue antigen. Sometimes the rejection occurs after days or weeks due to cell mediated cytotoxicity or antibody mediated mechanisms. Sometimes delayed rejection takes place i.e., after several years because immuno deposition occurs in vessels which result in fibrosis of organ.