Question

            Define and describe the following terms:

a.         Eosinophils:

b.         Natural Killer cells:

c.         Platelets:

d.         Interlukins:

e.         Interferon:

Answer 1

a. EOSINOPHILS

Eosinophils are granulocytic white blood cells that paly an important role in the defense against parasitic infection. Eosinophils are composed of a bilobed nucleus and numerous cytoplasmic granules which stain with acidic dyes, hence also called acidophiles. The granules contain chemical mediators which are released following eosinophil activation during parasitic infections. Eosinophils constitiute about 1-4% of thetotal white blood cells. They ar motile phagocytic cells that play important roles in mediating immune responses in allergy and asthma.

b. NATURAL KILLER CELLS

Natural Killer Cells (NK cells) are small group of large granular lymphocytes that plays an important role in innate immunity.The exhibit cytotoxic activity against a wide range of tumor cells and some types of virus infected cells. They play analogous roles to cytotoxic cells in adaptive immune responso. But they differ from cytotoxic cells in that they possess the ability to recognize tumor or virus infected cells in the absence of any antigen specific receptors ( Cytotoxic cells require priming by antigen presenting cells). Hence they anamed as 'natural killer' cells

c. PLATELETS

Platelets or thrombocytes are small colourless non nucleated cells that are formed elements considered to be tye fragments of cytoplasm. They paly an impotant role in blood clotting mechanism. They are derived from the megakaryocytes in the bone marrow which circulate in an inactive state. Upon activation, they release certain chemical substances which carry out their functions. the functions of platelets include blood clotting, blood retraction, hemosatasis, repair of ruptured blood vessels along with role in defense mechanism.

d. INTERLEUKINS

Interleukins are a group of cytokines secreted by various immune cells that play important role in regulating body's response to infection.These are secreted rapidly by cells in response to infection. Once secreted, it travels to its target cells and binds to it by the cell membrane receptor iniatating a casacade orf reactions that ultimately alters the cells behaviour. They are typically referrred to by numbers like IL-1, IL-2,IL-3, etc each one carrying out a specific function which include T cell stimulation, Chemoattraction of T cells, promoting growth of mast cells etc.

e. INTERFERONS

Interferons are a group of cytokines that pay important role during viral infection. These are generally secreted by the virus infected cells that enables the nearby cells to increase their antiviral defences.They are so called because of their ability to interfere with viral replication thereby protecting cells from the spread of infection. Another function of interferons is the upregulation of antigen presenting molecules (MHCs) on antigen presenting cells