• The way an individual's body responds to the infection is known as the host response.

• The body responds by:

- Sending certain cells to the infection site (cellular defenders)

- Making biochemical substances to counteract the foreign invaders

• Loss of immune function is deadly to the body.

• E.G., AIDS

• HIV disables a specific group of immune cells

• HIV+ individuals often develop infections from microorganisms that rarely cause infections in ppl with healthy immune systems

• The immune system can become so intense in it's response that it begins to harm the body that it is trying to protect.

• An overzealous response of the immune system happens in periodontitis.

Components of the immune system that play an important role in combating periodontal disease

• Cellular defenders (phagocytes, lymphocytes)

• The complement system

• Act like independent single-cell organisms

• Can move thru tissues & capture microorganisms on their own

• 2 types that are important to perio disease are:

-Polymorphonuclear leukocytes (PMN's)

-Monocytes/macrophages

• AKA neutrophils

• Rapid responders, provide the 1st line of defense

• Capture & destroy bacterial invaders

• Short-lived cells; die when they become engorged w/ bacteria

• Attracted to bacteria by process called chemotaxis

• PMN's contain many strong bacteriacidal & digestive enzymes, called lysosomes

• Perio pathogens are most effectively destroyed by PMN's.

• Called monocytes when they enter the bloodstream

• Called macrophages when in the tissues

• Slower to arrive at the infection site than PMN's

• Surround and destroy bacteria

• Long lived cells seen in chronic inflammation

• Small leukocytes that help defend the body

• 2 main types are:

- B lymphocytes (B cells)

-T lymphocytes (T cells)

• Once activated, makes millions of antibodies & pours them into the bloodstream

• Can differentiate into 2 types of B cells:

- Plasma B Cells

- Memory B Cells

• Y shaped proteins

• One end of the Y binds to the outside of the B cell

• The other end of the Y bonds to a microorganism and helps to kill it.

• Antibodies are known collectively as immunoglobins.

- IgM

-IgA

IgD

IgG

IgE

(MADGE)

What are T lymphocyte (T cells)?

• The main function is to intensify the response of other immune cells (macrophages, B lymphocytes) to the bacterial invasion.

• T cells make substances called cytokines that further stimulate the immune response.

Cytokine- A general name for any protein that is secreted by cells and affects the behavior of nearby cells.

• A complex series of proteins circulating in the blood that works to

- facilitate phagocytosis of bacteria

- kill bactera directly by forming pores in bacterial cell membranes.

• Destruction of pathogens

• Osponization of pathogens

• Recruitment of phagocytes

• Immune clearance

• Components of complement can destroy certain microorganisms directly by forming pores in their cell membranes

• For this task, the complement system makes a protein called the membrane attack complex

• This protein can puncture cell membranes of certain bacteria (lysis)

• The complement system facilitates the capture and destruction of bacteria by phagocytes.

• This process is called opsonization of pathogens.

• Complement components coat the surface of bactera, allowing the phagocytes to recognize,engulf, and destroy bacteria.

• opsonization is the most important action of the complement system

• To fight an infection, leukocytes travel thru the bloodstream.

• The thin layer of epithelial cells that line the interior surface of blood vessels is called the endothelium.

• Near the infection site, leukocytes push their way between the endothelial cells (extravasation) & enter the connective tissue.

• This process is called transendothelial migration.

• Chemotaxis is process whereby leukocytes

- Enter the connective tissue

- Are attracted to the site of the infection in response to biochemical comounds released by the invading bacteria

• Biologically active compunds secreted by cells that activate the body's inflammatory response

• Mediators of importance in periodontitis include

- Cytokines

- Prostaglandins

- Matrix metalloprotienases

• Leukocytes secrete cytokines that play a major role in regulating the behavior of immune cells.

• Chemokines- a subroup of cytokines- cause additional immune cells to be attracted to the site of an infection or injury

• Acute inflammation

• Chronic inflammation

• A short-term, normal process that protects and heals the body

• The acute inflammation process is achieved by the increased movement of plasma and leukocytes from the blood into injured tissues

1. Heat- A localized rise in temp due to an increased amount of blood at the site

2. Redness- The result of increased blood in the area

3. Swelling- The result of accumulation of plasma and leukocytes at the site

4. Pain- Excess fluid in the tissues puts pressure on sensitive nerve endings, causing pain

5. Function loss- Result of swelling and pain

• Blood vessels near the infected site become more permable

• PMN's are the 1st cells to arrive at the site

• PMN's release cytokines

• The liver makes C-Reactive protein (CRP)

• If the body succeeds in eliminating all the microorganisms, the tissue wil heal & inflammation will cease.

• If not, the inflammatory response becomes chronic.

• A long lived, out of control inflammatiory respoinse that continues for more then a few weeks

• it's a pathological condition that can destroy healthy tissue and cause more damage then the original problem

• The classic warning signs seen in acute inflammation are absent here

• Problem can go unnoticed by the pt

• Clinically, pain is often absent

• Because the body can't rid itself of invading organisms

• Invading microorganisms are persistant and stimulate an exaggerated immune response.

• When inflammation becomes chronic, the inflammatory response can become so intense that it does permanant damage to the body tissues, as in periodontitis.

• Chronic inflammation is characterized by an acculmation of macrophages

• Macrophages engulf and digest microorganisms

• Leukocytes release inflammatory mediators that perpetuate the inflammatory response.

• Tissue damage is the hallmark of chronic inflammation

• Associated w/ a number of disease conditions:

-Rheumatoid arthritis

- Diabetes

- Asthma

- Gingivitis

- Periodontitis

• Signs & symptoms of chronic inflammation may partially or completely disappear during a period of remission.

• The signs and symptoms may recur in all of their severity in an active period of disease known as exacerbation.

• Chemical mediators are biogically active compounds secreted by cells that activate the body's inflammatory response.  Important mediators include:

- IL-1, IL-6, and IL-8

- Leukotrienes

- Prostaglandins

- TNF-alpha