The final stage of the disease process (although it may not be the final stage of the infection) is the actual production of disease. Many microorganisms live in or on the body without causing disease. These organisms are called commensal organisms and may be beneficial to the host: the production of lactic and lactobacilli proprionic acidophilus in the vagina inhibits the growth of many other bacteria and many commensal organisms compete with pathogens for ‘living space’ in the gut. Microbial pathogens differ in that they cause dis- ease by one or more mechanisms like picture bellow. These include the following: (more…)

Routes by which infectious organisms gain entry into the body include the skin, respiratory tract, gastro-intestinal (GI) tract and GU tract. There are fundamentally two ways in which infectious agents cross the physical and chemical barriers: either they are able to penetrate the intact barriers at one or more anatomical sites, or the physical barriers are damaged and breached, allowing entry of the organism.

Bellow are some possibles pathogens entry into human body:

Penetration of intact skin or mucosa

• Skin. Few organisms are able to penetrate intact skin. However, some parasites (e.g. hookworm) or their larvae (e.g. schistosoma) can do this. Other agents, such as wart viruses, set up infection in the skin and do not enter further into the body.

• Mucosa. Mucosa, being softer and damper than skin, are much more frequent sites of entry and all intact mucosa can be penetrated by some organisms. Examples are shown in table bellow. Pathogens can cross epithelia by passing through epithelial cells, as in the case of the meningococcus (a bacteria causing meningitis), or by passing between the epithelial cells, seen with Haemophilus influenzae.

Mucosal Sites of Entry for Pathogens

Penetration of damaged skin or mucosa

There are many ways in which skin or mucosa can be damaged, allowing entry of infectious organisms that could not cross intact skin or mucosa. Damage to skin is a particularly important route of infection and can occur in a number of ways:

• Burns. Burns, especially severe ones, pose a major risk for infection, particularly with Staphylococcus, Streptococcus, Pseudomonas and Clostridium tetanus.

• Cuts and wounds. These can allow entry of similar organisms to those seen after burns.

• Insect bites. Numerous infections pathogenesis are transmitted via insect bites. These include malaria, typhus and plague.

• Animal bites. Animal bites can provide direct transmission of infection, such as in rabies. Because they cause significant damage to the skin, bites can allow the entry of the same environmental pathogens as burns, cuts and wounds (see above).

• Human behaviour. Various aspects of uniquely human behaviour can result in the skin being penetrated. Sharing of syringes by intravenous (IV) drug users exposes them to risk of hepatitis and human immunodeficiency virus (HIV). A number of viral infections (hepatitis, HIV) have been transmitted by blood transfusion and blood products (e.g. factor VIII for haemophiliacs) before appropriate screening procedures were developed. Transplantation has also resulted in transmission of infection before the introduction of appropriate donor screening.

Damage to mucosa may not increase the likelihood of infection to the same extent as damage to the skin. However, physical or chemical damage may allow entry of some organisms (e.g. smoking increases the risk of respiratory bacterial infections or respiratory allergies). Furthermore, infection of the mucosa with a virus may cause damage and facilitate the entry of bacterial pathogens spread.

There are thousands of components to the immune system, and during the course of learning about some of these it can appear that the immune system is far more complex and complicated than necessary for achieving what is, on the surface, the simple task of eliminating an infectious organism. There are a number of reasons why the immune system is complex. The first of these is the desirability of eliminating pathogens without causing damage to the host. Getting rid of a pathogen is theoretically easy. If you had an infection in your liver you could produce a nasty toxin that would kill the pathogen; unfortunately it would also destroy your liver. Killing pathogens is not difficult, but getting rid of pathogens without damaging the host is much more complicated. (more…)

The immune system consists of proteins, cells and organs that are concerned with defense of the individual, primarily against the threat of disease caused by infectious organisms. An infectious organism that causes disease is called a pathogen and the individual (person or animal) that is infected by a pathogen is called the host. Not all infectious organisms cause disease and some are actually beneficial, for example bacteria living in the gut help to digest certain foods. Infectious organisms that help the host are called commensalism organisms. (more…)

B cells

The main function of B cells is to produce antibodies. Antibodies are complex molecules produced by the immune system in response to antigens. As mentioned previously, antigens are foreign proteins or glycoproteins (a sugar linked to a protein) that trigger the immune response. Every living cell produces several different proteins, each unique to its own cell type and species. The antibody produced against the antigen is entirely specific to that antigen. (more…)

Human body treated all of the food that we ate, either plants or animals, as foreign substances. It is body immune system’s function to protect us from foreign material’s intrusion which may causes harmful to us. Then why does our immune system not oppose and refuse foreign materials that we consume as food?”

Naturally, if our body totally reject those foods which get into our body, we could not survive! Then, what is it that allows for food to plainly evade the roadblock of immune cells and be taken up into our bodies? In the final process, food become an integral part of our tissues and organs, and then be used as fuel for essential body processes. Research has begun to reveal part of the answer to this important issue in our body complex immune system question: the complex series of events known as oral tolerance. (more…)

It is estimated that more than 12 millions of American are having food allergy. About 4 percent of adults are having this disease and nearly 6 to 9 percent children under the age of 3 are having the same illness. The prevalence of food allergies is rising, where the most common food allergy in children are caused by milk allergy in children, eggs, peanuts allergy and tree nuts. In adults, the most common allergic reaction are triggered by peanuts, tree nuts, shellfish, fish and eggs. (more…)

Antibodies which are also known as immunoglobulin are found in our blood and other bodily fluids. Antibodies are used as a mechanism by natural immune system to identify, counteract, and neutralize foreign objects which are entered our body. B Cells is the first cell reacted when foreign objects entered our body and triggered the first alarming mode of immune system. It then try to recognize it and subsequently will proceed in the antibody production. There are five different types of antibody produced: IgA, IgG,IgM, IgE and IgD. Bellow we will discuss B Cells in antibody production process and three of the most prominent antibodies: IgA, IgM, and IgG.

B Cells in Antibody Production Process

B cells main function is in the process of antibody production. As you probably know, antibodies are complex structured molecules as result of body immune systems in response to antigens which are entered our body. Antigens are foreign subtracted objects which are mainly (more…)