MONOCLONAL ANTIBODIES

explain clonal selection

it is the clonal proliferation of B cells

cells triggered by contact with antigen can undergo successive waves of proliferation rapidly to build numbers

results in large number of genetically identical plasma cells all making antibody of the same specificity as the parent cell

when does an antibody antigen associaton occur

when the paratope (antigen binding site) on an antibody binds to an epitope (antigenic determinant) on an antigen

define affinity

the strength of binding of a single paratope to a single epitope

what does a high affinity mean in terms of shape/fit

high affinity means the shapes fit closely together

define specificity

the ability of antibody to distinguish between antigens

describe the relationship between antibody specificity and affinity

if the difference in affinity between closely related antigens increases then the specificity increases

describe cross reactivity

when an antibody may react with an epitope that did not stimulate its production

define polyclonal

directed towards a number of epitopes

define monoclonal

one type of antibody directed to one epitope

explain how monoclonal antibodies are produced

animal infected with antigen

response occurs

spleen of animal removed and B cells taken out

B cells mixed with myeloma cells, resulting in mix called hybridoma

cells screened for producing antibody to antigen

cells cultured and frozen

what are the different cell fusions that can occur

B cell to B cell

Cancer cell to cancer cell

B cell to cancer cell (hybridoma)

how can nucleotides be made

De novo pathway

Salvage pathway

how can de novo nucleotide pathway be inhibited

by aminopterin

explain the salvage pathway of nucleotide formation

requires source of hypoxanthine and thymine

incorporation needs hypoxanthine guanine, phopshoribosyl transferase (HGPRT) and thymine kinase

how are hybdriomas selected for

we grow cells on a HAT media (hypoxanthine, aminopterin and thymidine)

aminopterin prevents de novo pathway

no HGPRT made in cancer cells so cancer cell-cancer cell fusions die

b cell - b cell fusions not immortal so they die

hybridomas remain

what are monoclonal antibodies used in

often used as primary antibodies in assays; e.g. ELISA, RIA, western blot etc

why are monoclonal antibodies useful in therapies

they selectively target an epitope, so we can target the disease without damagin the host

what are humanised monoclonals

when the Fab portion of rodent antibodies is attached to the Fc portion of human antibodies

what is rituximab

a chimeric monoclonal antibody directed against CD20

used to remove B cells (e.g. B cell lymphomas, leukaemia, transplant rejection)

often used in conjuction with chemo