clinical study of immune response to

immunology was originally concerned with resistance to harmfulsubstances ( antigens ) . The immune mechanism classically Is dividedinto specific ( acquired ) and non-specific (innate ) mechanisms . Non-specific defence mechanisms are present from birth and do not dependupon previous experience of any particular antigens . Phagocytosis is themost important non-speciffic defence mechanism .Specific mechanisms are responsible for producing antibodies orsensitized cells that have the capacity to recognize I react with andneutralize the offending antigen .The immune response comprises all the complex series of events whichoccur as a result of the specific interaction of a cell with antigen .There are two broad categories of immune response :(1) Cellular immunity: ( or cell mediated immunity) which is mediated byspecifically sensitized Iymphocytes .(2) Humoral immunity the production and secretion of humoral antibodies(immunoglobulins that have been synthesized by antibody -formingcells or plasma cells .The immune system originated from stem cells in bone marrow , someof these cells migrate to thymus , known as thymus -dependent cells or T-Iymphocytes ,other cells do not reach the thymus , but can reach to bursa ,known as thymus -independent cells or B-Iymphocytes , which areresponsible for production of antibodies . Both T and B Iymphocytescirculate in the blood stream and can recirculate from blood throughlymphoid tissues into lymph and back to blood via the large lymph ducts.The effect of exposure to anaesthetic agents and surgical trauma onthe individual can alter the immune response directly or by releasingcorticosteroids or catecholamines in response to stress .