Immunology Pathways Quiz

Study Notes

Three complement activation pathways: Classical (by antibodies), Lectin (by lectins), and Alternative (spontaneous activation due to lack of inhibitors).
C3 protein is central, leading to formation of C3a and C3b.
Opsonization occurs when C3b coats pathogens, enhancing phagocytosis.
C5b initiates the formation of the Membrane Attack Complex (MAC) which lyses target cells.
C5a enhances inflammation by stimulating histamine release and attracting phagocytes.

Fever is characterized by abnormally high body temperature as a response to invading microorganisms.
Leukocytes release pyrogens that act on the hypothalamus to elevate body temperature.
Moderate fever benefits the body by sequestering iron and zinc, hindering microorganism growth, and increasing metabolic rate for faster repair.

The adaptive immune system protects against infections and abnormal cells, amplifies inflammation, and activates the complement system.
Requires prior exposure to specific foreign substances to become effective.
Characteristics include specificity, systemic nature, and memory for rapid response to known antigens.

Humoral Immunity: Involves antibodies that bind to pathogens, marking them for destruction; targets extracellular pathogens.
Cellular Immunity: Involves lymphocytes that attack infected cells directly or indirectly; targets intracellular pathogens.

Antigens provoke an immune response and mobilize adaptive defenses; most are large, complex, and foreign molecules.
Complete antigens have immunogenicity (stimulate lymphocyte proliferation) and reactivity (interact with lymphocytes and antibodies).

Small molecules that are not immunogenic by themselves but can trigger an immune response when combined with body proteins.
Examples include poison ivy and cosmetics.

Only specific parts of antigens, known as antigenic determinants, are recognized by antibodies and lymphocyte receptors.
Natural antigens have various determinants, eliciting responses from multiple lymphocyte populations.

Self-antigens, such as MHC proteins, are non-antigenic to the individual but can provoke an immune response in others during transfusions or grafts.
MHC proteins present antigens to T lymphocytes, crucial for immune recognition.

Two main types of lymphocytes: B lymphocytes (humoral immunity) and T lymphocytes (cellular immunity).
Antigen-presenting cells (APCs) assist in initiating immune responses without directly responding to specific antigens.

Lymphocytes originate in red bone marrow and undergo maturation before circulating through secondary lymphoid organs.
Activation involves antigen encounter, leading to proliferation and differentiation into effector (plasma) cells and memory B cells for future responses.