So what is happening in my body on this Journey of UCTD? As
I have said in the earlier blogs and in the ones about allergies, the body has
the ability to recognise something as foreign and attempts to get rid of it. The
allergen gets attacked by the white blood cells and produces an inflammatory response.
This process is called inflammation.
Thus the inflammatory response takes place when there is injury to the
cells from micro-organisms, any physical or chemical agents as well as those perceived
as foreign in the body.
Physiology of inflammation
Inflammatory response is the body’s natural defence
mechanism. It protects by neutralising and destroying any toxic substances. It
helps to limit the spread of these toxins to other parts of the body and
restore homeostasis. There are 4 main characteristics of inflammation –
redness, swelling, heat and pain. If inflammation occurs over a part that is
involved in mobility then it also will cause restriction or loss of mobility of
that part.
When injury occurs, and in case of UCTD the injury is caused
by the damage to connective tissue which is not recognised as self, a number of
changes take place to form the inflammatory response. The site will release
substances like histamine and bradykinin. Histamine is released from any
injured cells that contains it as well as by in response to the chemicals
produced by neutrophils (a type of white blood cell). Bradykinin is help to
attract neutrophils to the site of injury. There is also an increase in the
production of chemicals called prostaglandins. These prostaglandins are potent
vasodilators and they enhance the effect of histamine and bradykinin.
These chemicals increase dilation of the blood vessels causing
more blood to flow into the area. This gives redness to the area. It also
increases the permeability of the blood capillaries allowing fluid and
defensive substances to ooze out into the extra cellular space of the
surrounding tissues. This causes the swelling seen in the inflammatory
response. The defensive products are white blood cells and clot forming
chemicals. The white blood cells will destroy any micro-organisms, damaged
tissue and foreign substances. The increased blood supply also helps to remove
the toxins and dead cells from the site. A clot forms around the site to
prevent the micro-organisms and its toxins from spreading.
Another response by the body is to increase metabolism and
heart rate so that blood can reach the injured site quickly. The warmth at the
site of inflammation is due to the warm blood gathering in the area as well as increased
metabolism. The other symptom, pain, occurs due to the irritation of nerve
endings by the toxic chemicals and due to pressure caused by the swelling. Prostaglandin
also intensifies and prolongs the pain caused during inflammation. The
bradykinin also causes the intense pain by affecting the nerve endings. I will
discuss pain in more detail in another blog.
Lastly the loss of function or mobility can take place if
this inflammation is over or near a joint, its tendons and ligaments.
What does this mean in UCTD?
Once we understand what normally happens in the body as a defence
then we can understand what happens in UCTD. Within this autoimmune disease
which has not differentiated into any specific kind, the entire body’s
connective tissue is open to having an antigen – antibody response. This means
there can be injury due to this antigen-antibody response and inflammation will
result. So from the realms of general body defence we move to understand the
specific body defence.
What is Immune response?
When the resistance is specific to a disease or organism
then it is called immunity. When a particular antigen (organism or protein)
enters the body and it is recognised as foreign, the body will produce an
antibody specific to that antigen. Mostly antigens are proteins of some kind, nucleoproteins,
lipoproteins, glycoproteins and some large polysaccharides. With regards to bacteria
the flagella, the wall and even the toxins can be the antigen, but non
microbial kind varies widely, from pollen, egg white, nuts, oils, perfumes,
incompatible blood cells to transplanted organs.
Antibodies are formed against specific sites on the surface
of the antigen. Generally antigens are substances that are not usually part of
the body. The body has the capacity to recognise itself and so only substances
that are ‘non self’ will stimulate antibody production. Need I point out that
this is where things go haywire in UCTD? The body cannot differentiate between
self and non self, and thinks the connective tissue is an antigen!
The antibody produced is also a protein that is able to
combine with a specific antigen. The collective name for antibodies is
immunoglobulins as the antibodies are made of proteins called globulins. There
are 5 types of immunoglobulins – IgG (increases phagocytosis, neutralizes
toxins and protects foetus and new born), IgA (provides protection on the
mucosal surface), IgM (effective against microorganisms), IgD (stimulated the
antibody production) and IgE (participate in an allergic reaction). These also
can be not recognised by the body and can produce antibodies of its own.
When the antibody attaches itself to the antigen, it forms the
antigen-antibody complex that the body will destroy and remove. When the
antigen happens to be ‘self’ then it will produce an inflammatory response to
this perceived injury to its tissue.
So where is this connective tissue in the body?
Connective tissue is formed by cells and large amount of
intercellular matrix and extracellular elements. It forms the framework,
connecting, supporting and packing tissue in the body. There are 6 types of
connective tissues:
Tissue with cells floating in a fluid matrix – Blood.
Tissue with cells in a semi-solid matrix – mesenchyme, found in embryo and subsequently gives rise to all other connective tissue.
Tissue with cells in semi-solid matrix with a fine network of reticular fibres in the extracellular space. The tissue forms a 3 dimensional framework for organs such as spleen, bones and lymph nodes. The cells within are capable of ingesting particles, that is they are phagocytes.
Tissue with cells in semi-solid matrix with thicker collagenous and elastic fibres. These are 5 types –
·
Loose Fibrous tissue which form the packing
between organs, sheaths of muscles, nerves and blood vessels.
·
Dense Fibrous tissue which is strong and
inelastic but pliable and is found in ligaments, capsules of joints and heart
valves.
·
Elastic tissue is strong, flexible and
extensible and found in blood vessels and air passages.
·
Adipose tissue contains fat and forms a
protective cushion around the organs as well as function as an insulating layer
in the skin.
·
Tendon is tough and formed by inelastic cords of
dense fibrous tissue that allows muscles to be attached to bones.
Tissue with cells in solid elastic matrix with fibres – cartilage which is also of 3 different kinds-
·
Hyaline cartilage which is firm yet resilient
and us seen in air passages and ends of bones at joints.
·
White fibro-cartilage is tough but resistant to
stretching and found between vertebrae where it acts as shock absorber.
·
Elastic or Yellow fibro-cartilage is more
flexible but resilient and found in larynx and the ear.
T Tissue with cells in a solid rigid matrix which is impregnated with calcium and magnesium salts – bone, which forms the rigid framework of the body.
T Tissue with cells in a solid rigid matrix which is impregnated with calcium and magnesium salts – bone, which forms the rigid framework of the body.
Making sense of UCTD
Now you can connect all three sections – connective tissue, immune
response and the process of inflammation and it will give you a fair
understanding of what is happening to the body in an autoimmune disease. When
specific connective tissue involvement is there, it gives a particular pattern
of symptoms and changes to blood constituents and so categorised to a
particular autoimmune disease. However, luckily or unluckily, within
Undifferentiated Connective Tissue Disease there is no specific pattern or
blood changes and so does not allow a specific diagnosis. It is almost as if
the body has not decided on which parts are not self. The symptoms fluctuate
randomly between various symptoms and so we say that the disease has not differentiated
itself.
One must not assume that the title reflects the inability of
the medical profession to make a diagnosis. It is actually a disease in its own
right and pretty difficult to pin down as there is no pattern of either the
symptoms or of blood and body changes. However, the inflammatory response is
seem pretty strongly and can comprise of the whole body. You can look back at
the symptoms I have described in the previous blogs to make sense of the pathophysiology
of this disease. The medical profession do take a long time to make a diagnosis
not only because the investigation results fluctuate but also it takes time for
the disease to develop and most would rather wait and see than label the
disease immediately. About a quarter of the patients are likely to achieve
remission and be disease free. About a quarter will develop and differentiate into
one or 2 specific diseases over 5 years. The rest will remain in the undifferentiated
category.