The document provides an introduction to immunology and summarizes the three main types of immunity:
1. Barrier immunity: The skin acts as the first line of defense against pathogens through physical, chemical, and biological barriers.
2. Innate immunity: Nonspecific immunity present at birth that recruits immune cells, activates complement pathways, and identifies foreign substances to activate adaptive immunity.
3. Adaptive immunity: Highly specific immunity that develops after exposure to pathogens through lymphocytes. It provides long-lasting protection by distinguishing foreign from self but can also cause autoimmune diseases if it attacks the host's own molecules.
2. • Immunology: The study of Immune system
• Immune system: It’s the body defense
system against foreign entities such as
pathogens, antigens.
• In short, it remove everything from body
which should not be in the body. It can also
remove damaged or malignant cells
What are pathogens?
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5. 5
1. Barrier immunity:
Taking skin as an example:
• Skin is the outermost layer of the body with an extensive surface area of approximately 1·8 m2
• It is the first line of defense against a multitude of external pathogens and environmental insults
• The skin also has important homeostatic functions such as reducing water loss and contributing to
thermoregulation of the body
9. 2. Innate Immunity: Innate, or nonspecific, immunity is the
defense system with which you were born
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10. Major function of innate immunity
• recruit immune cells to infection sites by producing chemical factors, including
chemical mediators called cytokines
• activate the complement cascade to identify bacteria, activate cells, and promote
clearance of antibody complexes or dead cells
• identify and remove foreign substances present in organs, tissues, blood
and lymph, by specialized white blood cells
• activate the adaptive immune system through antigen presentation
• act as a physical and chemical barrier to infectious agents; via physical measures
such as skin and chemical measures such as clotting factors in blood
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11. 3. Adaptive immunity
• A type of immunity that develops when a person's immune system responds to a foreign substance or
microorganism, such as after an infection or vaccination.
• The function of adaptive immune responses is to destroy invading pathogens and any toxic molecules they
produce.
• The ability to distinguish what is foreign from what is self in this way is a fundamental feature of the adaptive
immune system.
• Unlike innate immune responses, the adaptive responses are highly specific to the particular pathogen that
induced them.
• They can also provide long-lasting protection.
• Any substance capable of eliciting an adaptive immune response is referred to as an antigen (antibody
generator) 11
12. 3. Adaptive immunity
• If the system fails to make this distinction and reacts destructively against
the host's own molecules. Such autoimmune diseases can be fatal.
• Allergic conditions such as hayfever and asthma are examples of
deleterious adaptive immune responses against apparently harmless
foreign molecules.
• Such inappropriate responses are normally avoided because the innate
immune system calls adaptive immune responses into play only when it
recognizes molecules characteristic of invading pathogens called pathogen-
associated immunostimulants
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The skin consists of three layers:
epidermis, a thin layer (approximately 0·1 mm thick). The stratified epithelium provides a watertight barrier from the external environment and prevents excessive water loss from the body. The epidermis is mainly composed of keratinocytes; however, there are also melanocytes, which provide a barrier from ultraviolet (UV) radiation through expression of melanin. The epidermis does not have a blood supply of its own, but instead is nourished from blood vessels below.
Dermis, a thicker layer (up to 3–4 mm depending on body site), which has a relatively low cell volume compared with the epidermis. The dermis predominantly consists of the extracellular matrix, such as collagen, which is made by fibroblasts. In addition to the extracellular matrix, the dermis contains structures such as blood vessels, lymphatics, nerves, sweat glands and pilosebaceous units.
The deepest layer of the skin is the subcutaneous layer, which consists of subcutaneous fat and connective tissue.
