immune system

Question 1

body needs to be able to recognise own cells so the immune system can identify….

Answer 1

• pathogens
• non-self material, such as cells from other organisms of the same species
• toxins, eg those produced by certain pathogens
• abnormal body cells such as cancer cells

Question 2

hoy lymphocytes recognise cells belonging to the body

Answer 2

• when foetus protected from infection due to protection from mother and placenta
• lymphocytes will exclusively collide with body’s own self material.
• the lymphocytes that have receptors that fit exactly that of the bodys own cells are suppressed or die
• only remaining lymphocytes are those that might fit foreign material (non- self)

in adults lymphocytes produced in the bone marrow initially only encounter self- antigens. All lymphocytes that show an immune response to these self- antigens undergo apoptosis (programmed cell death), before they can differentiate into mature lymphocytes

Question 3

macrophages

Answer 3

• scavengers which constantly move around to remove dead cells and “foreign invaders”.
• can be fixed or wandering
  -derive from haemopoietic stem cell in blood
• can activate further immune responses

Question 4

neutrophils

Answer 4

• more potent than macrophages- use chemicals, enzymes and nets to stop microbes
• most abundant type of w.b.c
• multi-lobbed nucleus to facilitate migration in and out of blood vessels as they move across tissues

Question 5

different antigen presenting cells

Answer 5

• cancer cells prevent antigens on cell surface membrane
• body cells invaded by viruses prevent some antigens on own cell surface membrane
• transplanted cell from organism of same species show foreign antigen
• phagocytes that have engulfed/ broken down a pathogen present some of the pathogen antigens on own cell- surface membrane

Question 6

cloned T cells:

Answer 6

• develop into cytotoxic T cells
• develop into memory cells that enable a rapid response to future infections by the same pathogen
• stimulate phagocytes to engulf pathogens by phagocytosis
• stimulate B cells to divide and secrete their antibody

Question 7

cytotoxic T cells

Answer 7

• kill abnormal cells and body cells that are infected by pathogens. Do this by producing perforin that makes holes in cell surface membrane of infected cells. Means membrane freely permeable to all substances so cell dies as a result

Question 8

how antibodies lead to destruction of antigen

Answer 8

• antibodies dont destroy antigens directly, but prefer the antigen for destruction by phagocytosis.
• cause agglutination, by clumping bacterial cells together so makes it easier for phagocytes to locate them as they are less spread out throughout the body. This is possible as each antibody has two antigen binding sites
• serve as markers that stimulate phagocytosis to engulf the bacterial cells to which they are attached
• precipitation of soluble antigens. Soluble antigens are held together to form precipitates

Question 9

what is a monoclonal antibody

Answer 9

• antibody produced by a single clone of cells that is complementary to only one specific antigen

Question 10

monoclonal antibodies in cancer treatments

Answer 10

• direct monoclonal antibody therapy: MABs produced are specific to antigens on cancer cells. These are given to patient and attach themselves to receptors on cancer cells. They block the chemical signals on the cancer cells that stimulate uncontrolled growth. This form of therapy is non toxic and highly specific so lead to fewer side effects
  -indirect monoclonal antibody therapy. Involves attaching a radioactive or cytotoxic drug to the monoclonal antibody so when attaches to cancer cell, it kills the cancer cells. These can be given in smaller doses so are cheaper and also reduce any side effects that the drug may have

Question 11

why is HIV considered a retrovirus

Answer 11

-uses reverse transcriptase enzyme to convert RNA into DNA, which is then sent to the cells nucleus