Practice question

Somatic cell fusion underlying hybridoma merges two differentiated cell types each contributing specialized traits necessary monoclonal antibody manufacturing. Antigen-experienced B lymphocyte harvested spleen four days after final booster carries functionally rearranged Ig heavy VDJ and light VJ genes formed RAG1/RAG2 recombination junctional diversity somatic hypermutation conferring high affinity specificity target epitope active transcription intronic enhancer Emu 3 prime regulatory region capacity synthesizing Ig up to 2000 molecules per second but limited lifespan due lack telomerase dependence T-cell help CD40L IL-4 IL-21 undergoing Fas-FasL activation-induced cell death few divisions. Plasmacytoma myeloma line P3X63Ag8.653 lacking HPRT enzyme secreting no endogenous Ig provides immortal growth due chromosomal translocation t(12;15) placing c-myc under IgH enhancer driving continuous cycle plus HAT selection sensitivity enabling elimination unfused myeloma. PEG induced membrane fusion allows cytoplasmic mixing forming heterokaryon subsequently nuclear fusion mitotic segregation retaining chromosomes encoding antibody variable regions B cell while myeloma chromosomes sustain uncontrolled proliferation. Selection eliminates unfused myeloma primary B cells permitting only hybridoma colonies producing monoclonal antibody exquisite specificity and immortality essential scale manufacturing.