Definition Of Defense Against Damages..
The local response of the tissues to damage, no matter how the damage is caused, is called inflammation. The features of inflammation are redness, warmth, swelling and pain, and because of these an impairment of function of the wounded area. When living tissues are damaged, chemical substances are liberated in the area and produce a dilatation of the local small vessels, arterioles, capillaries and venules, and a corresponding increase in the local blood supply (redness and warmth). The distended venules also become more permeable so that plasma leaks through their walls and floods the wound (swelling or oedema). Certain white blood cells (polymorphonuclear leucocytes) in the plasma act as scavengers, destroying any foreign material in the wound and any tissues damaged beyond repair, while other cells with the help of the plasma proteins construct new tissues to repair the defect. Pain is produced by the action of the chemical substance on the nerves, as well as by the original trauma. Acute inflammation may have several outcomes:
1. Resolution when complete return to normality occurs occasionally, as in lobar pneumonia
2. Healing by fibrous (scar) tissue, as in wounds
3. Chronic inflammation when the changes take a long time to settle down
4. Death of tissue (necrosis)a word which applies to the death of relatively small numbers of cells or gangrene, which applies to the death of a large area such as a digit or even a limb
Immunity
Immunology may be defined as the study of the ability of the tissues of an individual (host) to recognize and subsequently react to foreign substances (antigens).
The immune response comprises:
I. Recognition that the material is foreign (an antigen)
2. Primary reaction against the antigen
3. Stored memory in the tissues of contact with the antigen
4. Specific and altered (usually enhanced) reaction to the antigen upon subsequent exposure
The whole response is a function of the host lymphoid tissue, by which is meant the tissues in which white blood cells other than the polymorpho¬nuclear leucocytes are formed. Lymphoid tissue occurs in lymph nodes, spleen, thymus, tonsil and intestine.
Recognition. During fetal life, the individual is thought to learn to react against its own tissues. This phenomenon is called tolerance. Under certain circumstances individuals can be made tolerant of foreign antigen. One way of inducing tolerance is by giving repeated injections of very small amounts of antigen: an example is the process of desensitization by a course of injections of the offending pollen for sufferers from hay-fever.
The primary reaction may be mediated by serum antibodies or by cells. Some antigens stimulate the plasma cells in the lymphoid tissue to secrete antibodies, which are special proteins (immunoglobulins) which circulate in the plasma. Antibody reacts with specific antigen, in such a way that the antigen is more easily eliminated from the body by poly¬morphonuclear leucoeytes.
Examples of antibody-mediated immunity are the protection of normal people against tetanus or typhoid by the injection of weakened forms of the organisms that produce these diseases, leading to the development of circulating antibodies. The immune response takes several days to develop, and is called active immunity.
Another way in which antibody-type immunity can be used is to protect the individual by injection of antibody (e.g. plasma, or a concentrate of the appropriate fraction of the plasma protein) from another immunized
i
individual passive immunity. This technique s used to treat diphtheria and tetanus.
Cell-mediated immunity is a form of immune response in which no circulating antibodies can be detected; it is probably a function of the small lymphocytes. Classical examples are the response of the body to tuberculosis, e.g. the Mantoux test, p. 204, and the rejection of grafts from foreign donors. In a period of about a week after grafting, the neighbouring lymph nodes swell and show a rapid increase in their content of small lymphocytes; then similar white cells invade the graft and it is destroyed by an inflammatory reaction. A subsequent graft from the same foreign donor is rejected much more rapidly because the host is now sensitized (immune).
Auto-immunitY Failure of tolerance results in an individual attacking his own tissues by making antibodies to them. This phenomenon of auto- immunity is known to be implicated in a variety of diseases including Hashimoto's thyroiditis, rheumatoid arthritis, myasthenia gravis, and probably many others.
Surgical applications
( I ) immunization. The production of active or passive immunity against various infective organisms has been discussed above.
(2) Blood transfusion. The importance of the antigens which define human blood-groups, and the cross-matching techniques that are used to determine whether a particular donor's blood is suitable for trans¬fusion into a particular recipient are discussed.
(3) Tissue- and organ-grafting. Recent advances in this field have been spectacular. The transplantation of a kidney is now quite a common procedure; several liver transplantations have been performed, as well as the more controversial cardiac transplants. New hope has been given to sufferers from chronic diseases of essential organs.
The technical problems of the surgical operations required have been largely solved. There remain the inter-related problems of providing suitable donororgans and avoiding rejection of the graft by the host.
The local response of the tissues to damage, no matter how the damage is caused, is called inflammation. The features of inflammation are redness, warmth, swelling and pain, and because of these an impairment of function of the wounded area. When living tissues are damaged, chemical substances are liberated in the area and produce a dilatation of the local small vessels, arterioles, capillaries and venules, and a corresponding increase in the local blood supply (redness and warmth). The distended venules also become more permeable so that plasma leaks through their walls and floods the wound (swelling or oedema). Certain white blood cells (polymorphonuclear leucocytes) in the plasma act as scavengers, destroying any foreign material in the wound and any tissues damaged beyond repair, while other cells with the help of the plasma proteins construct new tissues to repair the defect. Pain is produced by the action of the chemical substance on the nerves, as well as by the original trauma. Acute inflammation may have several outcomes:
1. Resolution when complete return to normality occurs occasionally, as in lobar pneumonia
2. Healing by fibrous (scar) tissue, as in wounds
3. Chronic inflammation when the changes take a long time to settle down
4. Death of tissue (necrosis)a word which applies to the death of relatively small numbers of cells or gangrene, which applies to the death of a large area such as a digit or even a limb
Immunity
Immunology may be defined as the study of the ability of the tissues of an individual (host) to recognize and subsequently react to foreign substances (antigens).
The immune response comprises:
I. Recognition that the material is foreign (an antigen)
2. Primary reaction against the antigen
3. Stored memory in the tissues of contact with the antigen
4. Specific and altered (usually enhanced) reaction to the antigen upon subsequent exposure
The whole response is a function of the host lymphoid tissue, by which is meant the tissues in which white blood cells other than the polymorpho¬nuclear leucocytes are formed. Lymphoid tissue occurs in lymph nodes, spleen, thymus, tonsil and intestine.
Recognition. During fetal life, the individual is thought to learn to react against its own tissues. This phenomenon is called tolerance. Under certain circumstances individuals can be made tolerant of foreign antigen. One way of inducing tolerance is by giving repeated injections of very small amounts of antigen: an example is the process of desensitization by a course of injections of the offending pollen for sufferers from hay-fever.
The primary reaction may be mediated by serum antibodies or by cells. Some antigens stimulate the plasma cells in the lymphoid tissue to secrete antibodies, which are special proteins (immunoglobulins) which circulate in the plasma. Antibody reacts with specific antigen, in such a way that the antigen is more easily eliminated from the body by poly¬morphonuclear leucoeytes.
Examples of antibody-mediated immunity are the protection of normal people against tetanus or typhoid by the injection of weakened forms of the organisms that produce these diseases, leading to the development of circulating antibodies. The immune response takes several days to develop, and is called active immunity.
Another way in which antibody-type immunity can be used is to protect the individual by injection of antibody (e.g. plasma, or a concentrate of the appropriate fraction of the plasma protein) from another immunized
i
individual passive immunity. This technique s used to treat diphtheria and tetanus.
Cell-mediated immunity is a form of immune response in which no circulating antibodies can be detected; it is probably a function of the small lymphocytes. Classical examples are the response of the body to tuberculosis, e.g. the Mantoux test, p. 204, and the rejection of grafts from foreign donors. In a period of about a week after grafting, the neighbouring lymph nodes swell and show a rapid increase in their content of small lymphocytes; then similar white cells invade the graft and it is destroyed by an inflammatory reaction. A subsequent graft from the same foreign donor is rejected much more rapidly because the host is now sensitized (immune).
Auto-immunitY Failure of tolerance results in an individual attacking his own tissues by making antibodies to them. This phenomenon of auto- immunity is known to be implicated in a variety of diseases including Hashimoto's thyroiditis, rheumatoid arthritis, myasthenia gravis, and probably many others.
Surgical applications
( I ) immunization. The production of active or passive immunity against various infective organisms has been discussed above.
(2) Blood transfusion. The importance of the antigens which define human blood-groups, and the cross-matching techniques that are used to determine whether a particular donor's blood is suitable for trans¬fusion into a particular recipient are discussed.
(3) Tissue- and organ-grafting. Recent advances in this field have been spectacular. The transplantation of a kidney is now quite a common procedure; several liver transplantations have been performed, as well as the more controversial cardiac transplants. New hope has been given to sufferers from chronic diseases of essential organs.
The technical problems of the surgical operations required have been largely solved. There remain the inter-related problems of providing suitable donororgans and avoiding rejection of the graft by the host.
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