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(6) What is skin ageing
and fibrosis
Long term irritation by certain untoward factors, such
as topical application of steroid preparations, alcoholic
or other therapeutic agents onto the skin can cause damage
to the skin with hyper-proliferation of the connective
tissue, this is called skin ageing and fibrosis. The features
of the skin in such condition are thickening and hardening
of the skin. The hyper-proliferated connective tissue
can compress the micro-vasculature, and thus decrease
the blood supply to the skin.
(7) What is isomorphic
reaction (Koebner's phenomenon)
In vitiligo patients any injury to the normal skin, such
as cut wound, burns, mosquito bites, and infection, will
cause the appearance of new lesions at the site of injury
after healing. This is called isomorphic reaction, also
called Koebner's phenomenon. Traditional Chinese medicine
believes that this is caused by imbalance of yin and yang,
and derangement of qi and blood; Western medicine believes
that it is the result of immunologic reaction. Skin injury
→ melanocyte damage → antigen release → recognition of
auto-antigen by auto-antibodies → immune response → new
lesions.
(8) What is rebound
reaction
After the use of steroids and certain other agents for
the treatment, the condition will improve. But the lesions
will re-appear and even be worse than before after the
discontinuation of therapy. White patches enlarge.
(9)What is immunity,
what is antigen and what is antibody
1) Immunity. Immunity is a function of the body to recognize
and eliminate foreign antigenic substances. The functions
of the immune response include:
① Immunologic defense: Under normal circumstances immune
system can defend the body against invasion by miroorganisms,
etc and neutralize toxins. Under abnormal circumstances,
an over-reactive immune system can cause hypersensitivity
while a depressed or absent response will cause immune
deficiency.
② Homeostasis: Under normal conditions the body constantly
eliminate damaged or effete cells within the body to maintain
normal physiological functions. Derangement of homeostasis
will lead to autoimmune disorders (The occurrence of vitiligo
is related to such derangement which results in elimination
of normal self melanocytes and the formation of white
patches of the skin).
③ Immunologic surveillance. Under normal conditions the
immune cells of the body, mainly T cells can search and
dispose (kill, destroy) the small number of abnormal cells
that may appear within the body. With a depressed immunologic
surveillance function the body can not control the occurrence
of cancer. See table 4 for normal and abnormal immune
response.
Tab 4. Normal and abnormal immune response
|
Functions
|
Normal response (normal
function)
|
Abnormal response
(Abnormal function)
|
| Immunologic defense |
Defense against invasion
of pathogens |
Hypersensitivity, immune
deficiency |
| Homeostasis |
Elimination of damaged
or effete |
Autoimmunity |
| Immunologic surveillance |
Search and eliminate abnormal
cells, e.g. malignant cells |
Tumors |
2) Antigens Antigen is a kind of substance that can stimulate
the human or animal immune system to initiate a series
of response by the production of immune substances such
as antibodies or sensitized T cells, and is capable of
specific in vivo and in vitro reaction with the relevant
antibodies or sensitized T cells. Thus, antigens have
dual effects: immunogenecity-to stimulate the immunologic
response by the body, and immune reactivity - specific
reaction with the immune substances thus produced.
The majority of antigens are foreign substances, such
as pathogenic microoganisms (bacteria, virus, and parasites)
and their products, animal serum products, etc. The farther
the relations between animal species, the greater the
difference in structure, the higher the antigenecity.
For different individuals of the same species there exist
certain differences in cells and tissue. For example,
in the humans there are ABO blood types on the red blood
cells, and blood type match tests must be done before
transfusion. On the nucleated cells and white blood cells
there are histocompatibility antigens which can cause
rejection reaction in allogeneic skin grafting and organ
transplantation (This is why other people's skin can not
be used for epidermal grafting in the treatment of vitiligo).
Under normal circumstances the body's own tissue is not
antigenic and is not an antigen, and no response can be
induced by the production of antibodies, etc. But by the
action of many factors, such as trauma, infection, ionizing
radiation, drugs, noxious chemical substances, and heavy
metals. The structure of the self tissue will be altered
and become antigenic. These altered auto-antigens will
stimulate the immune system of the body, leading to autoimmune
diseases.
3) Antibody Antibody is formed by the body under the stimulation
of antigens and is a type of globin that can specifically
react with the antigen. It exists in the blood, lymph
and tissue fluids. Antibody was formerly called gamma
globins, but in 1964 the specialist committee under the
World Health Organization renamed all proteins with antibody
activity and antibody related proteins immunoglobins.
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