HYPERSENSITIVITY REACTIONS
Hypersensitivity reactions are antibody-mediated. Antigens are fixed and intrinsic to the tissue in which
the reaction is occurring. Antibodies are directed against the antigens that are expressed on the cell
surface or on the surface of some extracellular layer like the glomerular basement membrane or the
alveolar-based membrane. There are autoantibodies directed against red blood cells (RBCs), which
belong to the blood group antibodies, and these antibodies can destroy RBCs at body temperature, 37
degrees Celsius. This is because the other antibodies will attack and destroy the RBCs at low
temperature, which helps the RBC destruction at low temperature. Antibodies directly leading to
phagocytosis lead to the production of opsonizing molecules that coat the cell, and then there is
facilitated phagocytosis. C3b is also an opsonizing molecule because it has a receptor on the phagocytes.
What is happening is that, in the first example, C3b binds with the cell, and then on one side, it releases
histamine, which causes inflammation; and on the other side, it releases granules called "cytokines" that
cause an immune response.
The point in this category is that an antibody is not depleted or destroyed, for example, by the
membrane attack complex or depleted by facilitated phagocytosis. Antibodies can also be partially
activated by the complement system and produce C3b and C3d, which act as opsonins. ADCC is the
condition in which ADCC occurs as a result of antibody-dependent cellular cytotoxicity. The tissue-
damaging immune response of the antibody-mediated response against the fixed intrinsic antigen takes
two forms: in the first case, cells are depleted or destroyed, but there is no inflammation; in the second
case, there is inflammation. The third mechanism is different; these two are distinct from each other.
Autoimmune diseases are diseases in which the body's own immune system attacks and destroys its own
cells. One type of autoimmune disease is glomerulonephritis, which is a condition in which the walls of
the small blood vessels in the kidneys become inflamed. Autoimmune reactions can also cause
hematuria (blood in urine) and proteinuria (a high level of protein in the urine). In some cases, these
reactions can lead to hemoptysis (a bloody discharge from the lungs).
Autoimmune reactions can also occur in other parts of the body, such as the heart. This type of
autoimmune reaction is called a type 2 hypersensitivity reaction. In this reaction, there is no destruction
or depletion or inflammation - simply cell dysfunction, cell or tissue damage. Another example is insulin
resistance diabetes mellitus, a condition in which the body's cells do not respond properly to insulin.
If you experience a breakout or your skin starts to feel dry and itchy, it is likely that you are developing a
fungal infection. Your skin might also develop multiple blisters as a result of the infection.
Hypersensitivity reactions are antibody-mediated. Antigens are fixed and intrinsic to the tissue in which
the reaction is occurring. Antibodies are directed against the antigens that are expressed on the cell
surface or on the surface of some extracellular layer like the glomerular basement membrane or the
alveolar-based membrane. There are autoantibodies directed against red blood cells (RBCs), which
belong to the blood group antibodies, and these antibodies can destroy RBCs at body temperature, 37
degrees Celsius. This is because the other antibodies will attack and destroy the RBCs at low
temperature, which helps the RBC destruction at low temperature. Antibodies directly leading to
phagocytosis lead to the production of opsonizing molecules that coat the cell, and then there is
facilitated phagocytosis. C3b is also an opsonizing molecule because it has a receptor on the phagocytes.
What is happening is that, in the first example, C3b binds with the cell, and then on one side, it releases
histamine, which causes inflammation; and on the other side, it releases granules called "cytokines" that
cause an immune response.
The point in this category is that an antibody is not depleted or destroyed, for example, by the
membrane attack complex or depleted by facilitated phagocytosis. Antibodies can also be partially
activated by the complement system and produce C3b and C3d, which act as opsonins. ADCC is the
condition in which ADCC occurs as a result of antibody-dependent cellular cytotoxicity. The tissue-
damaging immune response of the antibody-mediated response against the fixed intrinsic antigen takes
two forms: in the first case, cells are depleted or destroyed, but there is no inflammation; in the second
case, there is inflammation. The third mechanism is different; these two are distinct from each other.
Autoimmune diseases are diseases in which the body's own immune system attacks and destroys its own
cells. One type of autoimmune disease is glomerulonephritis, which is a condition in which the walls of
the small blood vessels in the kidneys become inflamed. Autoimmune reactions can also cause
hematuria (blood in urine) and proteinuria (a high level of protein in the urine). In some cases, these
reactions can lead to hemoptysis (a bloody discharge from the lungs).
Autoimmune reactions can also occur in other parts of the body, such as the heart. This type of
autoimmune reaction is called a type 2 hypersensitivity reaction. In this reaction, there is no destruction
or depletion or inflammation - simply cell dysfunction, cell or tissue damage. Another example is insulin
resistance diabetes mellitus, a condition in which the body's cells do not respond properly to insulin.
If you experience a breakout or your skin starts to feel dry and itchy, it is likely that you are developing a
fungal infection. Your skin might also develop multiple blisters as a result of the infection.
