Question

Compare and contrast innate and adaptive immunity by explaining how they differ is the following 2 questions (I-III). Please answer in complete sentences. How do these 2 types of immunity differ is the timing of their response? How do the receptors as innate and adaptive immune cells differ in what they recognize? Please describe what the receptors on immune cells recognize and what the receptors on adaptive immune cells recognize. Complement proteins normally circulate in the blood and provide early protection from infection by pathogens. Why do complement proteins not damage healthy cells or tissues despite being widely present in the blood? If an individual has a genetic mutation that causes a deficiency in only the C3 complement protein, which activation pathway or pathways (Classical, Leetin, and/or Alternate) would be affected? Please justify your answer. Describe how the B-cell receptor and the T-cell receptor differ in the way that they bind antigens? Erythrocytes (i.e., red blood cells) lack the expression of Major Histocompatibility Complex (MHC) class I proteins on their cell surface. Why don't NK cells kill antologous (i.e., self-derived) red blood cells?

Answer 1

12.

12(i). Innate means present from birth. Innate type of immunity is generally inherited from parents and passed to offspring. Innate immunity is a type of non - specific defense mechanisms which occurs immediately after exposure to infection. This system activates within minutes to hours after a foreign agent attacks within the human body. It does not arise from the earlier infection or vaccination. The innate immune response is activated by chemical properties of the antigen. It comprises two lines of defenses – first line of defense and second line of defense. First line of defense consists of skin (the epidermis), gastric acid in the stomach and mucus membranes. Like, nasal mucus membrane serves as a filter to stop the inward movement of large particles. Second line of defense consists of chemicals and cells that are released in the blood after being exposed to a pathogenic stimulus.

Adaptive immunity is a type of acquired immunity and refers to antigen-specific immune response. Adaptive immunity is not passed from the parents to offspring, hence it cannot be inherited. It consists of antibody responses and cell mediated responses. The adaptive immunity takes time to develop. The antigen first must be processed and recognized. Once an antigen has been recognized, the adaptive immune system creates an army of immune cells specifically designed to attack that antigen. Adaptive immunity also includes a "memory" that makes future responses against a specific antigen more efficient.

12 (ii). Receptors present on innate immune cells are phagocytic, chemotactic etc. Phagocytic receptors stimulate ingestion of the pathogens they recognize. Chemotactic receptors are produced by bacteria and guides neutrophils to sites of infection.

Adaptive immune cells consist of antibody responses and cell-mediated responses, which are carried out by different lymphocyte cells - B cells and T cells respectively. B cells are the major cells involved in the creation of antibodies that circulate in blood plasma and lymph, where they bind specifically to the foreign antigens. Binding of antibody inactivates viruses and microbial toxins by blocking their ability to bind to receptors on host cells.

13. Complementary proteins are those incomplete protein sources that together form a high quality complete protein. It will provide the missing protein in certain amino acids like lysine where protein is low in quantity. Together, these two proteins provide all of the essential amino acids that one’s body needs to function properly. Beans and rice are an example of complementary proteins. Complementary proteins does not damage healthy cells or tissues despite being widely present blood because they play an essential role in the cellular maintenance, growth, and functioning of the human body and serves as the basic structural molecule of all the tissues in the body.

14. C3 complement protein is a protein of the immune system which plays a fundamental role in the complement system and contributes to innate immunity. C3 is required for opsonisation (the coating of pathogenic cells with opsonin to facilitate phagocytosis). If an individual as a genetic mutation that causes a deficiency in only the C3 complementary protein then the classical activation pathway would be affected. Activation pathway (AP) is activated when the C3b protein directly binds a microbe. Other elements of the AP are factor B, factor D and properdin. It can also be triggered by foreign materials and damaged tissues. A defect in the pathway that results in deficiency of C3 can lead to problems with opsonisation.

15. B and T cell receptors are specific for particular antigen. B and T cell receptors are differ in their structure, the genes that encode them and type of epitope to which the bind.

B cell receptors are transmembrane receptor protein located on the outer surface of B cells. B cell receptors binds intact antigen.

T cell receptors is a molecule found on the surface of T lymphocytes that is responsible for recognizing fragments of antigen as peptides bound to major histocompatibility complex (MHC) molecules. The binding between T cell receptor and antigen peptides is of relatively low affinity and is degenerate.