Other humoral effectors and humoral factors have the ability to lyse microorganisms directly. The best studied of these are a class of small peptide antibiotics known as defensins, which in their active forms are all roughly 30 amino acids long (3,5 kilodaltons), positively charged, and protease-resistant. Each also has three internal disulfide bonds. They are classified as either α or β defensins based on the arrangement of the disulfides, but both classes have nearly the same compact, folded structure consisting of three strands of antiparallel β-pleated sheets. (more…)

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…)

There are several pathogen types that can cause disease include many groups of single-celled microorganisms and larger multicellular parasites. Viruses, bacteria, some yeasts, and protozoan parasites are examples of single- celled pathogens. Fungi and helminths (parasitic worms) are the major multi-cellular pathogens. These pathogens come from very different parts of the biological kingdom and vary considerably in many aspects. Pathogens differ enormously in their size. They also have very different lifestyles and cause disease in a variety of ways like bellow:

Poliovirus (Viruses)

Size: 20–400nm
Habitat: Intracellular: pharynx, intestine, nervous system
Mode of multiplication: Intracellular synthesis of viral components
Multiplication rate (doubling time): <1 hour

Poxvirus (Viruses)

Size: 20–400nm
Habitat: Intracellular: upper respiratory tract, lymph nodes, skin
Mode of multiplication: Intracellular synthesis of viral components
Multiplication rate (doubling time): <1 hour

Streptococcus pyogenes (Bacteria)

Size: 1–5µm
Habitat: Extracellular: pharynx
Mode of multiplication: Cell fission
Multiplication rate (doubling time): 3 hours

Mycobacterium leprae (Bacteria)

Size: 1–5µm
Habitat: Intracellular: macrophages, endothelial cells, Schwann cells
Mode of multiplication: Cell fission
Multiplication rate (doubling time): 2 weeks

Candida albicans (Fungi)

Size: 2–20µm
Habitat: Extracellular: mucosal surfaces
Mode of multiplication: Asexual budding
Multiplication rate (doubling time): Hours

Histoplasma capsulatum (Fungi)

Size: 2–20µm
Habitat: Intracellular: macrophages
Mode of multiplication: Asexual budding
Multiplication rate (doubling time): Hours

Trypanosomes (Protozoan parasites)

Size: 1–50mm
Habitat: Extracellular: bloodstream
Mode of multiplication: Binary fission
Multiplication rate (doubling time): 6.5 hours

Plasmodium (Protozoan parasites)

Size: 1–50mm
Habitat: Intracellular: red blood cells, hepatocytes
Mode of multiplication: Asexually in hepatocytes (cell fission)
Multiplication rate (doubling time): 8 hours

Ascaris lumbricoides (Metazoan parasites worms)

Size: 3mm to 7m
Habitat: Intestine
Mode of multiplication: Lays eggs
Multiplication rate (doubling time): 200000 eggs/day

Taenia solium tapeworm (Metazoan parasites worms)

Size: 3mm to 7m
Habitat: Gut
Mode of multiplication: Releases body segments containing eggs
Multiplication rate (doubling time): 800000 eggs/day

Size of pathogens

One feature of the range of pathogenic organisms listed above is the enormous variation in size. Viruses are the smallest infectious organisms, being 20–400 nm in size. At the other end of the scale some parasitic worms, such as the tapeworm, can be up to 7 m (20 ft) in length. This represents a difference in scale of a factor of 10e9 . To put that into some sort of perspective, if a virus were the size of a tennis ball, a fully developed tape- worm would reach from London to Los Angeles. It does not stretch the imagination too far to appreciate that the problems posed to the immune system by these two organisms would require very different solutions.

Stages of disease production by pathogens

Size is not the only way in which infectious organisms vary. They also vary enormously with respect to how they enter and live within the body and actually cause disease. Infection and disease production by pathogenic organisms can be divided into four stages:

1. Invasion.
2. Multiplication.
3. Spread.
4. Production of disease (pathogenesis).

Although infection usually involves all of these steps, there are many exceptions in terms of both the steps involved and their order. Some pathogens do not spread significantly or even technically gain entry to the body. Organisms may replicate locally before spreading or may spread through the body before beginning significant replication. Pathogens show considerable variation at each of these stages of infection, as will be described below.

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…)

Atopic dermatitis is a chronic inflammatory condition of the skin which usually starts in infancy. It is sometimes called ‘atopic eczema’ or even simply ‘eczema’. Recently, the term ‘atopic eczema dermatitis syndrome’ or eczema symptoms or infantile eczema has also been proposed to indicate the varied nature of this disease. The diagnosis is based on clinical features of a chronic itchy dermatitis with typical morphology and distribution and a relapsing and remitting course. (more…)

The symptoms of asthma occur together with variations in the diameter of medium- size airways such that it is increasingly difficult to exhale. Narrowing of the airways can occur because of smooth muscle contraction, edema or swelling of the wall, or increased mucus in the airways. However, it is increasingly clear that the pathologic event underlying most cases of asthma is acute inflammation of the airway walls. (more…)

Our current knowledge for trigger factor and food allergy intolerance is still in it infancy level. We already known that the allergic intolerance are different for groups of people. Some individuals are less resistant in developing allergy than others. Allergic sensitivity or atopic allergic disease are heritable and this means that genetic factors is playing a critical role. But the latest researches reveal that it is not merely heredity factors, environmental also have significant impact for someone to develop allergy.

Allergy trigger in the form of food allergen are mostly fallen to some certain foods like milk, egg, peanuts, fish, soya and nuts. We are curios on what is so peculiar about allergens in food? (more…)

The main reason that your body has an immune system is for your survival. Without immune system, human body is a delightful place for microorganisms such as bacteria, viruses, fungi and parasites to live. The condition of your body is really conducive for microbes bacteria to grow. Your body is warm, moist and full of nutrients, this is the perfect condition for microbes bacteria to survive and reproduce. But do not expect gratitude from those microbes bacteria you have in your body system. Most of them have no idea what happens to you. Some of them can cause illness and some can be deadly. (more…)