CONCEPTS OF INFLAMMATION AND THE IMMUNE RESPONSE

LEARNING OUTCOMES

After studying this chapter, you should be able to:1. Describe the concept of self-tolerance2. Explain the differences between inflammation and infection3. Compare and contrast the cells, purpose and features of inflammation and

immunity4. Describe the basis for the five cardinal manifestations of inflammation5. Interpret a white blood cell count with differential to indicate no immune

problems, an acute bacterial infection, or an allergic reaction.6. Explain how complement activation and fixation assists in protection from

infection.7. Compare the cells, function, and protective actions of anti-body mediated

immunity for their protection effectiveness and duration of immunity

Injury and infectious diseases are common. Most people, however, are healthy more often than they are ill. Inflammation and immunity are the two major defenses that a protect a person against diseases and other problems when the body is invaded by organisms.

OVERVIEWImmunity is composed of many cell functions that protect people against the effects of injury or microscopic invasion. People interact with many other living organisms in the environment. The size of these organisms varies from large (other human and animals) to microscopic (bacteria, viruses, molds, spores, pollens, protozoa, and cells from other people or animals). As long as organisms do not enter the body’s internal environment, they pose no threat to health.The body has some defenses to prevent organisms form gaining access to the internal environment. These defenses are not perfect, and invasion of the body’s internal environment by organisms occurs often. Invasion occurs much more often than does an actual disease or illness because of proper immune functioning.

PURPOSE OF INFLAMMATION AND IMMUNITYThe purpose of inflammation and immunity is to neutralize, eliminate, or destroy organisms that invade the internal environment. To accomplish this purpose without harming the body, immune system cells use defensive actions only against non-self proteins and cells. Immune system cells can distinguish between the body’s own healthy self cells and other, non-self proteins and cells.

SELF VERSUS NON-SELF

Non-self proteins and cells include infected body cells, cancer cells, and all invading cells and organisms. This ability to recognize self versus non-self, which is necessary to prevent healthy body cells form being destroyed along with the invaders, is called self-tolerance. The immune system cells are the only body cells capable to determining self- from non-self. Self tolerance is possible because of the different kinds of proteins present on cell membranes.

All organisms are made up of cells. Each cell is surrounded by a plasma membrane. Many different protein protrudes through the cell’s membrane. For example, in liver cells, many different proteins are present on the cell membrane surface.

The amino acid sequence of each proteins are found on the liver cells of all animals (including humans) that have livers, because these protein types are specific to the liver and serve as a marker for liver tissues.

Other protein types are found only on the liver cells of humans, because these protein type are specific markers for humans. Still other protein types are found only on the liver cells of humans with a specific blood type.

In addition, each person’s liver cells have surface protein types that are specific to that person. These proteins are unique to the person and would be identical only to the proteins of an identical twins. These unique proteins, found on the surface of all the body cells of that individual, serve as a “Universal Product code” or a “cellular fingerprint” for that person. The proteins that make up the universal product code or a “cellular fingerprint” for that person.

The proteins that make up the universal product code for one person are recognized as “foreign” or non-self, by the immune system of another person. Because the cell-surface proteins are non-self to another person’s immune system, they are antigens, proteins capable of stimulating an immune response.

Human Leuckocyte antigens (HLAs) make up this unique universal product code for each person. “Leukocyte antigen” is not a correct term, because antigens are also present on the surfaces of nearly all body cells, not just on antigens only if they enter another person’s body. These antigens specify the tissue type of a person. Other names for these personal cellular fingerprints are human transplantation antigens, human histo-compatibility antigens, major histo-compatibility antigens, and class I antigens.

Organization of the Immune System

The immune system is not confined to any one organ or area of the body. Most immune system cells come from the bone marrow. Some of these cells mature in the bone marrow; other leave the bone marrow and mature in different body sites. When mature, most immune system cells are released into the blood, where they circulate to most body areas and have specific effects.

The bone marrow is the source of all blood cells, including immune system. The bone marrow produces an immature, undifferentiated cells called a stem cell . This immature stem cell is also described as pluripotent, multipotent and totipotent. These terms describe the potential future of the stem cell.

The maturation pathway of any stem cell depends on

Immune Regulation

Regulation of the immune response involves balance and counterbalance. Dysfunction of the natural immune system can occur when the immune components are inactivated or when they remain active long after the effects are beneficial. A successful immune response eliminates the responsible antigen.Immunodeficiencies are characterized by inactivation or impairment of immune compomentsm and disorders with an inflammatory component. (eg. Asthma, allergy, arthritis) are characterized by persistent inflammatory responses.

Acquired ImmunityAcquired (adaptive) immunity – immunologic responses acquire during life but not present at birth – usually develops as a result of prior exposure to an antigen through immunization (vaccination) or by contracting a disease.

Response to InvasionWhen the body is invaded or attacked by bacteria, viruses, or other pathogens, It has three means of defense:

The phagocytic immune response The humoral or antibody immune response The cellular immune response

The first line of defense, the phagocytic immune response, involves the WBCs (granulocytes and macrophages) which have the ability to ingest foreign particles. These cells move to the point of attack, where they engulf and destroy the invading agents.

Recognition Stage

Recognition of antigens as foreign, or non-self by the immune system is the initiating event in any immune response. The body must first recognize invaders as foreign before it can react to them.

Proliferation StageThe circulating lymphocyte containing the antigenic message returns to the nearest lymph node. Once in the node, the sensitized lymphocyte stimulates some of the resident dormant T- and B-lymphocytes to enlarge, divide, and proliferate.

Response StageIn the response stage, the differentiated lymphocytes function in either a humoral or a cellular capacity. The production of antibodies by the B-lymphocytes in response to a specific antigen begins the humoral response. Humoral refers to the fact that the antibodies are released into the bloodstream and therefore reside in the plasma (fluid fraction of the blood).

Effector StageIn the effector stage, either the antibody of the humoral response or the cytotoxic (killer) T-cell of the cellular response reaches and connects with the antigen on the surface of the foreign invader.

Humoral Immune ResponseThe humoral response is characterized by the production of the antibodies by B-lymphocyte is ultimately responsible for the production of antibodies, both the macrophages of natural immunity and the special T-cell lymphocytes of cellular immunity are involved in recognizing the foreign substance and in producing antibodies.

Antigen RecognitionSeveral theories explain the mechanisms by which B-lymphocytes recognize the invading antigens and respond by producing antibodies. It is known that B-lymphocytes recognize and respond to invading antigens in more than one way.

Role of AntibodiesNtibodies are large proteins called immunoglobulins (because they are found in the globulin fraction of the plasma proteins). All Immunoglobulins are glycoproteins and contain a certain amount of carbohydrate.