Human Immunity and Blood

Type IV hypersensitivity is cell-mediated (T-cells) and does not involve antibody-mediated phagocytosis or classical antigen presentation in the same way as humoral responses.

Type IV hypersensitivity is cell-mediated by T-lymphocytes and does not involve antibodies, unlike Types I, II, and III.

The T helper cells also known as CD$ _4^+$ release cytokines and trigger the activity of other immune cells.

In Type IV hypersensitivity, sensitized T-helper cells (specifically Th1 cells) are the first to arrive at the site and release lymphokines to recruit other cells.

Anaphylaxis, also known as anaphylactic shock is a serious allergic reaction that is rapid in onset and may cause death. It typically causes an itchy rash, throat or tongue swelling, shortness of breath, vomiting, lightheadedness, and low blood pressure. Common causes include insect bites and stings, foods, and medications.  The mechanism involves the release of mediators from certain types of white blood cells triggered by either immunologic or non-immunologic mechanisms.

A mast cell is a type of white blood cell that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems. Mast cells are primarily known for their role in allergy and anaphylaxis (shock). Mast cells play a key role in the inflammatory process. When activated, a mast cell can either selectively release mediators or compounds that induce inflammation, from storage granules into the local site.

Histamine is an organic nitrogenous compound involved in the inflammatory response and has a central role as a mediator of itching. Histamine causes vasodilation of peripheral blood vessels due to which there is increased blood flow to the site of inflammation. It mediates the inflammatory reaction by the release of other chemical mediators of inflammation and causes redness, swelling etc at the site of inflammation.

Immune complex-mediated hypersensitivity (Type III) involves the deposition of antigen-antibody complexes. These complexes are typically cleared from circulation by phagocytic cells, specifically monocytes and eosinophils, which help mitigate tissue damage.

A mast cell is a type of white blood cell that contains many granules rich in histamine and heparin. Mast cells play an important protective role in inflammatory and allergic reactions. When mast cells are activated, they release mediators or compounds that induce inflammation from storage granules into the local site and promotes the inflammatory response. In allergic reactions, mast cells remain inactive until an allergen binds to IgE already coated upon the cell.

• Shock is a life-threatening situation due to poor tissue perfusion with impaired cellular metabolism, manifested inturns by serious physiological abnormalities.
  
• Anaphylactic shock is also called as Type I immunogenic reaction.
• Anaphylactic shock is characterized High permeability of capillaries causing loss of fluid from the blood.
  
• Anaphylaxis symptoms usually occur within minutes of exposure to an allergen. 
  
• The most common anaphylactic reactions are to foods, insect stings, medications and latex.
  
• So, the correct answer is 'High permeability of capillaries causing loss of fluid from the blood'

Allergies, also known as allergic diseases are caused by hypersensitivity of the immune system to typically harmless substances in the environment. The mechanism involves immunoglobulin E antibodies (IgE) binds to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine. The release of histamine develops symptoms such as red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling.

Innate immunity also called natural or inborn immunity. Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body.

The immune system provides both the types of immune response innate and acquired immune responses. Innate immunity occurs naturally due to genetic factors or physiology. It is a native immune response that present by birth. It provides physical barrier such as skin, Physiological barriers such as pH of the stomach, bile juice, saliva and tears, cellular barriers such as leucocytes, macrophage cell and cytokine barrier.

The innate immune is an older evolutionary defense strategy  and it is dominant immune system response found in plants ,fungi,insects,and primitive multi-cellular organisms..The innate leukocytes includes: