Immunity Flashcards
What is immunology?
Immunology is a branch of biological and medical sciences that studies the immune systems in all organisms.
What is the immune system responsible for?
The immune system is responsible for the body’s ability to recognize and defend itself against invaders and their products. It works with cellular and chemical systems, as well as other systems like clotting, fibrinolytic cascades, nervous, and endocrine systems.
What are the three types of immune responses?
The three types of immune responses are the innate immune system, the adaptive immune system, and the smart system (which has memory and allows rapid response to a second encounter with a pathogen).
What is the role of primary lymphoid tissues in the immune system?
Primary lymphoid tissues educate adaptive immune cells to not recognize ‘self’, ensuring immune tolerance and preventing autoimmunity.
How does the innate immune system differ from the adaptive immune system?
The innate immune system is present from birth, is non-specific, has no memory, and responds quickly within seconds. In contrast, the adaptive immune system involves specific recognition of antigens and has a powerful memory to respond more rapidly during secondary encounters with pathogens.
What are the four types of defensive barriers in the innate immune system?
The four types of defensive barriers are:
Anatomical: Skin, mucous membranes.
Physiological: Body temperature, fever, acidity in the stomach.
Phagocytic: White blood cells that engulf pathogens.
Inflammatory: Response to infection or damage, with signs like redness, heat, pain, swelling, and loss of function.
What is the function of phagocytes in the immune response?
Phagocytes, such as macrophages and neutrophils, recognize and engulf pathogens or toxins to destroy them. This process can be oxygen-dependent or oxygen-independent.
What are inflammatory mediators and what do they do?
Inflammatory mediators include cytokines, chemokines, and various proteins that help regulate the immune response. They trigger inflammation, promote the migration of white blood cells to sites of infection, and help repair tissue damage.
How do dendritic cells contribute to the immune system?
Dendritic cells are antigen-presenting cells that process antigens and present them to T-cells, acting as messengers between the innate and adaptive immune systems.
What is the role of natural killer (NK) cells in immunity?
NK cells recognize and kill infected cells or tumor cells directly, without the need for antigen presentation. They use killer receptors and antibody-dependent cellular cytotoxicity (ADCC) to eliminate targets.
What is the difference between humoral immunity and cell-mediated immunity?
Humoral immunity involves B cells and the production of antibodies, while cell-mediated immunity involves T cells, macrophages, neutrophils, NK cells, and cytokines to target intracellular pathogens, viruses, and cancer cells.
What is an antigen and how does it interact with the immune system?
An antigen is any substance that binds to specific receptors on lymphocytes. It can be a protein, lipid, or carbohydrate from pathogens, pollen, or even ‘self’ molecules, triggering an immune response.
What are antibodies and what are their functions?
Antibodies are Y-shaped molecules produced by B cells. They bind to specific antigens, and their functions include activation of complement, neutralization of pathogens, opsonization, agglutination, and stimulation of inflammation.
What is the role of T helper cells in adaptive immunity?
T helper cells (CD4+) help activate other immune cells, including B cells for antibody production and cytotoxic T cells for killing infected cells. They recognize antigens presented by class II MHC molecules.
What is the function of cytotoxic T cells (CTLs)?
Cytotoxic T cells (CD8+) recognize antigens presented by MHC class I molecules and kill infected or tumor cells by releasing perforins and granzymes to induce apoptosis.
What is the immunological synapse?
The immunological synapse is the interaction between the T cell receptor on T cells and the antigen-Major Histocompatibility Complex (MHC) on antigen-presenting cells, leading to T cell activation.
How is T cell activation initiated?
T cell activation requires three signals:
Binding of the T-cell receptor to the antigen-MHC complex.
Co-stimulatory molecules on the antigen-presenting cell binding to T cell molecules.
Cytokines from the antigen-presenting cell, directing T cell differentiation.
What are the main functions of effector T cells?
Effector T cells produce cytokines to help other immune cells, including B cells and cytotoxic T cells, in their functions. They also carry out functions like targeting and killing infected cells or tumor cells.
What are the characteristics of memory cells in the immune system?
Memory cells are long-lived, antigen-experienced T or B cells that return to a resting state after being activated. They can be reactivated upon subsequent encounters with the same antigen, leading to a faster and stronger immune response.
What is the role of complement proteins in the immune response?
Complement proteins are a group of serum and cell surface proteins that help regulate immune responses, act as opsonins to increase phagocytosis, and lyse cells and microorganisms. They play a key role in inflammation and immune defense.
How does the body recognize pathogens during phagocytosis?
Phagocytes recognize pathogens through cell surface receptors that identify them as “foreign.” This can happen either directly through pattern recognition receptors (PRRs) binding to pathogen-associated molecular patterns (PAMPs) or indirectly through opsonization by serum proteins like antibodies or complement.
What is the function of chemokines in the immune system?
Chemokines are small proteins that guide the movement of white blood cells towards sites of infection or injury through chemotaxis. They bind to specific receptors on white blood cells, promoting their migration to areas where they are needed.
What are the differences between MHC class I and MHC class II molecules in antigen presentation?
MHC class I molecules present antigens to cytotoxic T cells (CD8+), while MHC class II molecules present antigens to helper T cells (CD4+). Class I molecules are found on nearly all nucleated cells, while class II molecules are primarily found on antigen-presenting cells like dendritic cells, macrophages, and B cells.
What is the process of opsonization, and how does it enhance immunity?
Opsonization is the process where serum proteins (like antibodies or complement proteins) coat pathogens, making them easier for phagocytes to recognize and engulf. This enhances the immune response by increasing the efficiency of pathogen destruction.
How do antibodies contribute to the neutralization of pathogens?
Antibodies neutralize pathogens by binding to critical parts of the pathogen, such as viral surface proteins, preventing the pathogen from attaching to and infecting host cells. This can block the pathogen’s ability to cause harm or enter cells.
