Examples of diseases with granulomatous inflammation.

• Tuberculosis  Caused by (Mycobacterium tuberculosis)
• Leprosy Caused by (Mycobacterium leprae)
• Syphilis Caused by (Treponema pallidum Gumma)
• Cat-scratch disease Caused by (Gram-negative bacillus)
• Sarcoidosis Unknown etiology 
• Crohn disease (inflammatory bowel disease) Caused by (Immune reaction against undefined gut microbes and, possibly, self antigens).

Mechanism of foreign body granuloma.

Foreign body granulomas are seen in response to relatively inert foreign bodies, in the absence of T cell–mediated immune responses. Typically, foreign body granulomas form around materials such as talc (associated with intravenous drug abuse), sutures, or other fibers that are large enough to preclude phagocytosis by a macrophage but are not immunogenic. Epithelioid cells and giant cells are apposed to the surface of the foreign body. The foreign material can usually be identified in the center of the granuloma, particularly if viewed with polarized light, in which it may appear refractile.

Mechanism of immune granuloma formation

Immune granulomas are caused by a variety of agents that are capable of inducing a persistent T cell–mediated immune response. This type of immune response produces granulomas usually when the inciting agent cannot be readily eliminated, such as a persistent microbe or a self antigen. In such responses, macrophages activate T cells to produce cytokines, such as IL-2, which activates other T cells, perpetuating the response, and IFN-γ, which activates the macrophages.

Tuberculosis is a prototype of immune granuloma.

Define granuloma with example.

Granulomatous inflammation is a form of chronic inflammation characterized by collections of activated macrophages, often with T lymphocytes, and sometimes associated with central necrosis. The activated macrophages may develop abundant cytoplasm and begin to resemble epithelial cells, and are called epithelioid cells. Some activated macrophages may fuse, forming multinucleate giant cells. Granuloma formation is a cellular attempt to contain an offending agent that is difficult to eradicate. In this attempt there is often strong activation of T lymphocytes leading to macrophage activation, which can cause injury to normal tissues. 

There are two types of granulomas.

• Immune Granulomas
• Foreign body Granulomas
  

Name different types of granulomatous inflammation.

 Different types of granulomatous inflammation are follows

• Foreign body
• Necrotizing granulomas
• Non-necrotizing granulomas 
• Suppurative granulomas
• Histiocytic response
  

Short Note On "Opsonin"

Opsonins are proteins which coated microbes to enchnace efficiency of phagocytosis.

The major opsonins are 

• Immunoglobulin (Ig)G antibodies, 
• The C3b breakdown product of complement activation, 
• Certain plasma lectins, notably mannose-binding lectin, 

all of which are recognized by specific receptors on leukocytes.

Outline the oxygen dependent mechanism of microbial killing.

Oxygen dependent microbial killing is caused by Reactive oxygen species (ROS)

Reactive Oxygen Species. ROS are produced by the rapid assembly and activation of a multicomponent enzyme, phagocyte oxidase which oxidizes NADPH and, in the process, reduces oxygen to the superoxide anion. In neutrophils, this oxidative reaction is tightly linked to phagocytosis,
and is called the respiratory burst. Phagocyte oxidase is an enzyme complex consisting of at least seven proteins. In resting neutrophils, different components of the enzyme are located in the plasma membrane and the cytoplasm. In response to activating stimuli, the cytosolic protein components
translocate to the phagosomal membrane, where they assemble and form the functional enzyme complex. Thus, the ROS are produced within the phagolysosome, where they can act on ingested particles without damaging the host cell. 

The azurophilic granules of neutrophils contain the enzyme myeloperoxidase (MPO), which, in the presence of a halide such as Cl−, converts H2O2 to hypochlorite, the active ingredient in household bleach. The latter is a potent anti-microbial agent that destroys microbes by halogenation or by oxidation of proteins and lipids. 

The H2O2-MPO-halide system is the most efficient bactericidal system of neutrophils. Nevertheless, inherited deficiency of MPO only causes a modest increase in susceptibility to infection, emphasizing the redundancy of microbicidal mechanisms in leukocytes. H2O2 also is converted to hydroxyl radical (OH•), another powerful destructive agent