Reflecting on the Lesson: Choose one concept in our lesson today, give a brief explanation about the concept and cite how would you apply this learning in your everyday life.
Since I was a little kid, there were days where my face and body were covered with “pantal” or hives, coupled with a stuffy nose, as well as occasional fevers. It usually occurs when I eat cashew nuts, when the weather changes drastically, or when I am subjected to immense stress. In the lesson today, I found out that these physiological manifestations can be classified as hypersensitivity, or the state of altered reactivity where the immune response reacts in an exaggerated manner to a particular agent. There are four (4) types of hypersensitivity, each with different characteristics and responses.
Type I (Anaphylactic) Reactions.
This type of hypersensitivity is considered the most common (often referred to as allergies) and the most rapid. In fact, exposure to a particular allergen can immediately trigger immune responses such as vasodilation, increased smooth muscle contraction, as well as heightened mucus secretion. In some occasions, responses can also involve hay fever, eczema, and hives. As such, my “allergies” are classified under this category of hypersensitivity.
Type II (Cytotoxic) Reactions.
These hypersensitivities are triggered by the antagonistic mechanism of IgG and IgM antibodies against the antigens of an individual’s blood or tissue cells. As an example, in incompatible blood fusions, the body’s antibodies (particularly IgG and IgM) are unable to recognize the antigen present in the newly transferred blood. This triggers a cytotoxic reaction, causing activation of complement and, eventually, the lysis of “foreign” cells.
Type III (Immune-Complex) Reactions.
This type of hypersensitivity involves IgA or IgM antibodies, as well as the amount of antigens present. In certain situations, antigens are not attached to a particular cell. As such, when antigen-antibody (immune) complexes form, they have a tendency to scatter across different structures, including blood vessels, kidneys, lungs, skin, and joints. As more of these immune complexes are deposited, they eventually activate complement and cause inflammation. Examples of this include Rheumatoid Arthritis and Glomerulonephritis.
Type IV (Cell-Mediated) Reactions.
Lastly, this category is also known as “delayed hypersensitivity,” and usually appears within 12 to 72 hours after exposure to the allergen. This reaction occurs when allergens are picked up by intraepidermal macrophages in the skin, which enables them to migrate into the lymph nodes. The allergens are then brought to T cells which, in turn, proliferate. This causes the activation of macrophages and tumor necrosis factors, which trigger an inflammatory response. Examples of allergens that trigger this response include poison ivy and Mycobacterium tuberculosis.
Altogether, knowing the different types and mechanisms of hypersensitivity helps us, especially those who possess physiological responses classified under these categories, fully understand the nature of the symptoms we experience. It guides us to make wise decisions, and to take the necessary measures to relieve such symptoms.