Cell Signalling + Immune Response Flashcards
How does the body prevent the entry of pathogens?
The body prevents pathogen entry through barriers such as skin (with high salinity, low pH, and antimicrobial secretions like sebum), mucous, tears containing lysozyme, and saliva from epithelial cells. Expulsive reflexes like coughing and sneezing also help, as well as hydrochloric acid in the stomach. Commensal bacteria on the skin and in the gut compete for nutrients to prevent pathogen growth.
What is the role of inflammation in the immune response?
Inflammation is a part of the non-specific immune response. Mast cells and basophils release histamines eg interleukins, causing blood vessels (arterioles) to dilate, leading to local heat and redness that reduce pathogen reproduction. Capillary walls become leaky, allowing plasma containing neutrophils and antibodies to leave the blood, causing swelling and pain to disable pathogens. Macrophages and neutrophils destroy pathogens through phagocytosis.
What are the different methods used by the body to destroy pathogens in the non specific immune response?
Methods include:
- Phagocytosis: chemotaxis attract phagocytes like neutrophils (granulocytes which can only ingest a few pathogens before death as they can’t regenerate lysosomes) and macrophages (derived from monocytes and have large capacity of ingesting pathogens and renewing lysosomes by migrating to infected tissues- accumulate at site of infection) engulf pathogens by endocytosis in phagosome vesicle and fuses with lysosomes which digest them, and present antigens on their surface using MHC proteins. Also produce cytokines in surrounding tissues which are useful in cell signalling to promote phagocytes to move to site of infection and stimulate specific immune response.
- Fever: Infected cells alert the hypothalamus to increase body temperature, reducing pathogen reproduction and improving the effectiveness of the immune response. May cause dehydration and denaturation of enzymes
- Opsonisation: Opsonins bind to receptors on pathogens, making them more recognizable to phagocytes eg immunoglobulin G
What are the components of the specific immune response?
The specific immune response involves lymphocytes (T and B cells), which are activated by antigens. T cells are produced by the bone marrow and mature in the thymus and are involved in cell-mediated immunity and humoral immunity, while B cells mature in the bone marrow and are involved in humoral immunity.
What are T lymphocytes, and how do they contribute to the immune response?
T lymphocytes are produced in the bone marrow and mature in the thymus. They have T cell receptors specific to certain antigens (similar structure to antibodies). When they bind to an antigen-presenting cell (APC) with the complementary antigen, they activate and undergo clonal selection and expansion, differentiating into Helper T cells or Cytotoxic T cells.
What are the functions of T helper cells?
T helper cells release cytokines in the humoral response to stimulate B cell maturation into plasma cells and memory B cells. In the cell-mediated response, they activate T killer cells and secrete opsonins to stimulate phagocytosis.
What do T killer (cytotoxic) cells do?
T killer cells travel around the body and attach to foreign antigens on infected cells. They secrete perforins that create holes in the infected cell’s membrane, allowing toxins to enter and kill both the cell and the pathogen inside.
What is the role of B lymphocytes in the immune response?
B lymphocytes mature in the bone marrow and are concentrated in lymph nodes and the spleen but also spread throughout the body. Each B cell can produce one type of antibody, which remains attached to the cell membrane. B cells replicate via clonal selection and expansion in the humoral response and differentiate into plasma cells or memory cells.
What are plasma cells, and what do they do?
Plasma cells are differentiated B cells that produce and secrete large quantities of antibodies into the blood, lymph fluid, gut or lungs. These cells are short-lived, but the antibodies they produce remain in the blood for a long time, aiding in the primary immune response (relatively slow). Have an extensive rER and ribosomes for antibody production.
What are memory cells, and how do they contribute to immunity?
Memory cells are long-lived cells that remain in the blood after an infection, providing immunological memory to specific antigens. They enable a faster and more effective secondary immune response if the same antigen is encountered again.
How do antibodies work in the immune response?
Antibodies are glycoproteins that bind to specific antigens on pathogens or infected cells. They can destroy pathogens by:
- Agglutination: Clumping pathogens together, preventing them from spreading and can easily undergo phagocytosis.
- Opsonisation: Making pathogens more easily recognizable to phagocytes by acting as opsonin
- Neutralization: Neutralizing effects of bacterial toxins by binding to them.
What is the humoral immune response?
The humoral immune response involves macrophages presenting antigens on their surface with MHC proteins to become antigen-presenting cells (APCs). T cells with receptors specific to this antigen triggers clonal selection when activated. T helper cells activate B cells that have engulfed the pathogen and become APCs by releasing cytokines to stimulate clonal selection. B cells then undergo clonal selection and differentiate into plasma cells or memory cells.
What is the cell-mediated immune response? When is it most useful?
In the cell-mediated response, T killer cells bind to infected cells presenting complementary antigens. They are activated by cytokines from T helper cells, clone themselves, and secrete perforin enzymes that cause pores to form in the infected cell membrane, leading to cell lysis and pathogen destruction. Any intact pathogens are labelled by antibodies. It is most useful when the pathogen is inside the cell.
What happens in the secondary immune response?
In the secondary immune response, if the antigen is encountered again, memory cells divide rapidly and differentiate into plasma cells and more memory cells, producing a faster and stronger immune response with more antibodies. Also includes T memory cells
What is lymph fluid, and what does it contain?
Lymph fluid is produced when some tissue fluid enters lymph capillaries, which have large pores to allow molecules to pass through therefore larger molecules which can’t pass through capillaries enter lymph vessels. It contains white blood cells (WBCs), transports lipids from the intestines to the bloodstream, and helps return lost plasma proteins. It also contains valves to prevent backflow.
What is the structure of antibodies?
GLobular glycoproteins- immunoglobulins
2 antigen binding sites means that more than one pathogen can bind to antibodies at the same time.
