Thursday, February 11, 2010
Humoral immunity is most effective against bacteria and viruses that live outside of cells (extracellular microbes). The immune cells that produce antibodies are a special lymphocytes called activated B cells or plasma cells.
Several steps are required for the production of antibodies.
1. A white blood cell called a macrophage ingests (eats) an invading microbe. The microbe is digested by the macrophage (see Figure 1). Some of the microbe's digested proteins (antigens) are displayed by the macrophage on its surface to alert other cells of the immune system that an invader is present.
Figure 1: Macrophage Digesting Microbe and Displaying Antigen
2. Lymphocytes called B cells also process and display the invader's proteins on their surfaces (see Figure 2).
Figure 2: B Cell Digesting Microbe and Displaying Antigen
3. When an immune cell called a T helper cell sees the same protein on the surface of a B cell and a macrophage, it sandwiches itself between the two other immune cells (see Figure 3). The formation of this bridge complex stimulates the B cell to begin dividing, making more copies of itself. The resulting group of activated B cells produces antibodies against the invading microbe's displayed proteins (antigens).
Figure 3: T Helper Cell Activates B Cell Causing B Cell Expansion and Antibody Production
The antibodies produced against an invader attach to antigens on its surface. The presence of antibodies on the surface of the invader serves as a "red flag" to the rest of the immune system and marks the invader for destruction. The killing takes place in one of two ways. The antibodies may cause leaks in the outer coat of the microbe; the leaky invader cannot recover and dies. More commonly, antibodies on the surface of the invader alert the killer cells of the immune system to ingest (eat) and destroy the invader.
Figure 4: Antibody Tags Microbe Marking It For Immune System Destruction
Antigen-antibody interactions are very specific. Antibodies produced in response to a specific antigen normally reactonly with that antigen. Antigen-antibody interactions are often likened to a lock and key. A given lock can only be "activated" by a matching key. Similarly, and a given antibody only reacts with its matching antigen.
Saturday, February 6, 2010
Monday, February 1, 2010
A heart attack (myocardial infarction) occurs when an area of heart muscle dies or is permanently damaged because of an inadequate supply of oxygen to that area.
Most heart attacks are caused by a clot that blocks one of the coronary arteries (the blood vessels that bring blood and oxygen to the heart muscle). The clot usually forms in a coronary artery that has been previously narrowed from changes related to atherosclerosis. The atherosclerotic plaque (buildup) inside the arterial wall sometimes cracks, and this triggers the formation of a clot, also called a thrombus.
A clot in the coronary artery interrupts the flow of blood and oxygen to the heart muscle, leading to the death of heart cells in that area. The damaged heart muscle loses its ability to contract, and the remaining heart muscle needs to compensate for that weakened area.
The risk factors for coronary artery disease and heart attack include:
· Too much fat in your diet
· Poor blood cholesterol levels, especially high LDL ("bad") cholesterol and low HDL ("good") cholesterol
· Male gender
Many of the risk factors listed are related to being overweight.
Newer risk factors for coronary artery disease have been identified over the past several years, including elevated homocysteine, C-reactive protein, and fibrinogen levels. High homocysteine can be treated with folic acid supplements in the diet. Studies are still ongoing about the practical value of these new factors.
Heart Attack Symptoms
Chest pain behind the sternum (breastbone) is a major symptom of heart attack, but in many cases the pain may be subtle or even completely absent (called a "silent heart attack"), especially in the elderly and diabetics. Often, the pain radiates from your chest to your arms or shoulder; neck, teeth, or jaw; abdomen or back. Sometimes, the pain is only felt in one these other locations.
The pain typically lasts longer than 20 minutes and is generally not fully relieved by rest or nitrioglycerine, both of which can clear pain from angina.
The pain can be intense and severe or quite subtle and confusing. It can feel like:
· squeezing or heavy pressure
· a tight band on the chest
· "an elephant sitting on [your] chest"
· bad indigestion
Other symptoms you may have either alone or along with chest pain include:
· Sweating, which may be profuse
· Feeling of "impending doom"
· Control your blood pressure.
· Control total cholesterol levels. To help with cholesterol control, your doctor may prescribe a medication of the statins group (atorvastatin, simvastatin).
· Stop smoking if you smoke.
· Eat a low fat diet rich in fruits and vegetables and low in animal fat.
· Control diabetes.
· Lose weight if you are overweight.
· Exercise daily or several times a week by walking and other exercises to improve heart fitness. (Consult your health care provider first.)
If you have one or more risk factors for heart disease, talk to your doctor about possibly taking aspirin to help prevent a heart attack.
After a heart attack, follow-up care is important to reduce the risk of having a second heart attack. Often, a cardiac rehabilitation program is recommended to help you gradually return to a "normal" lifestyle. Follow the exercise, diet, and medication regimen prescribed by your doctor.
SURGERY AND OTHER PROCEDURES
Emergency coronary angioplasty may be required to open blocked coronary arteries. This procedure may be used instead of thrombolytic therapy, or in cases where thrombolytics should not be used. Often the re-opening of the coronary artery after angioplasty is ensured by implantation of a small device called a stent. Emergency coronary artery bypass surgery (CABG) may be required in some cases.