bio unit 4 - immunity

Question 1

what is an antigen?

Answer 1

an antigen is a non-self molecule that triggers an immune response.

Question 2

cellular vs non-cellular pathogens

Answer 2

cellular - bacteria, protist, fungi, parasite
non-cellular - virus, viroid, prion

Question 3

what is clonal selection and how does it occur?

Answer 3

clonal selection is the reproduction and differentiation of a specific B cell. it occurs when antigenic fragments are presented to helper T cells that now activated release cytokines. the cytokines then stimulate a specific B cell that produces antibodies complimentary to the antigen to divide and form clones. most of these clones will develop into plasma B cells to produce the specific antibody, while the rest will differentiate into memory B cells to provide long term immunity.

Question 4

how do antibodies aid in the destruction of pathogens?

Answer 4

Precipitation - soluble pathogens become insoluble and precipitate
Agglutination - cellular pathogens become clumped for easier removal
Neutralisation - antibodies may occlude pathogen regions
Inflammation - antibodies may trigger an inflammatory response
Complement activation - complement proteins perforate membranes (cell lysis)

Question 5

how do allergens trigger a reaction?

Answer 5

plasma B cells create immunoglobulin E antibodies which attach to mast cells, triggering the release of histamine. histamine causes vasodilation, increased permeability of blood vessels, and attraction of leukocytes.

Question 6

what cells are involved in the innate/non-specific immune response?

Answer 6

natural killer cells, macrophages, nuetrophils, dendritic cells, mast cells, basophils, and eosinophils

Question 7

what cells are involved in the adaptive/specific immune response?

Answer 7

Helper T cells, cytotoxic T cells, plasma B cells, memory B cells

Question 8

explain humoral immunity

Answer 8

the humoral immune system deals with antigens from pathogens that are extracellular (freely circulating or outside of the infected cells). antigen fragments presented on MHC-2 markers are presented to Th cells which then release cytokines, triggering B cell clonal selection. Antibodies are created by plasma B cells to have a PANIC response. Memory B cells are created to retain long-term immunity against the pathogen.

Question 9

explain cell mediated immunity

Answer 9

cell mediated immunity occurs inside infected cells (intracellular). cancerous and virus-infected cells infect self-cells and thus are not recognised as foreign. they may present antigenic fragments with their own self markers (MHC-1). when Th cells identify them, they stimulate cytotoxic T cells which bind to the specific antigen and release perforin and granules, causing lysis of the infected cell’s membrane.

Question 10

what are the steps of phagocytosis?

Answer 10

1. the phagocyte is stimulated to bind to the pathogen
2. the phagocyte ingests the pathogen encasing it in a vacuole or vesicle
3. enzymes in the vesicle such as lysosomes break down the pathogen
4. the broken down phagocyte is excreted by exocytosis

Question 11

what is a macrophage?

Answer 11

a type of white blood cell that does phagocytosis and antigen presentation to T cells

Question 12

what is a dendritic cell?

Answer 12

an antigen presenting cell

Question 13

what is a neutrophil?

Answer 13

a white blood cell that does phagocytosis and degranulation

Question 14

what is an eosinophil?

Answer 14

a white blood cell that does granulation

Question 15

what is a natural killer cell?

Answer 15

a lymphocyte with granules and enzymes that can kill tumour cells or cells infected with a virus

Question 16

what is a mast cell?

Answer 16

a type of white blood cell that release histamine when triggered by an allergen

Question 17

what is a complement protein?

Answer 17

a protein that opsonizes pathogens, induces inflammatory response, and can destroy bacterial pathogens by lyses of the membrane

Question 18

what is an interferon?

Answer 18

a type of cytokine that is secreted by cells infected with a virus, they act on uninfected cells and make them more resistant to the virus

Question 19

what are the primary lymph organs?

Answer 19

the thymus and bone marrow

Question 20

where do T cells mature?

Answer 20

they migrate from the bone marrow and mature in the thymus.

Question 21

where do B cells mature?

Answer 21

they are created in the bone marrow and mature there also.

Question 22

what are the secondary lymph organs?

Answer 22

the lymph nodes and spleen

Question 23

types of acquired immunity:

Answer 23

active natural - being exposed directly to disease, prompting antibody and memory cell creation
active induced - being exposed to disease via vaccination, prompting antibody and memory cell creation.
passive natural - antibodies are gained directly and naturally, e.g. through breast milk
passive induced - antibodies are gained directly through medical induction, e.g. monoclonal antibodies (laboratory made)

Question 24

scientific strategies to control transmission:

Answer 24

quarantine, vaccination, face masks, hygiene

Question 25

social strategies to control transmission:

Answer 25

social distancing, education, changing behaviour