Hypersensitivity:
This can be defined as any immune response against a foreign antigen that is exaggerated beyond the norm. There are four main types of hypersensitivity response. Some people experience hypersensitivity to certain perfumes, wearing wool, or dusting furniture through sneezing, runny nose, or wheezing.
Figure 1 hypersensitivity
Mast cells:
Mast cells are specialized relatives of white blood cells, deriving from other stem cells in the bone marrow. They are distributed all throughout the body in connective tissues other than blood and mostly close to body surfaces including the skin and walls of the intestines and airways. They have a cytoplasm containing large granules loaded with a mixture of potent inflammatory chemicals such as histamine.
Herd immunity:
Herd immunity is the protection provided by all individuals in a population due to the inability of a pathogen to effectively spread when a large proportion of individuals (more than 75%) are resistant. The society can be provided with herd immunity when patients follow recommended immunization schedule.
Figure 3 herd immunity
Pseudomembranous colitis:
It is an infection caused by Clostridium difficile. In Pseudomembranoous colitis, large sections of the colon wall slough off, potentially perforating the colon, and leading to massive internal infection by fecal bacteria and eventually death.
Figure 4
REFERENCES:
Bauman RW. Microbiology with disease by Taxonomy. 3rd ed. San Francisco (CA): Pearson; 2011. 730p.
PICTURES:
Figure 3 http://theprimalparent.com/wp-content/uploads/2012/09/herd-immunity-slide-17.png
Figure 4 http://www.nejm.org/doi/full/10.1056/NEJMicm1004244
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