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#antigen

3 public questions tagged with this topic.

Immunological Applications

Rituximab targets which antigen?

MS4A1 gene on chromosome 11q12.2 encodes CD20 differentiation antigen, 33 to 37 kDa tetra-spanning membrane phosphoprotein with both N and C termini intracellular, four transmembrane helices forming tetrameric oligomer functioning as store-operated calcium channel component modulating B cell receptor induced calcium flux via interaction with calcium release-activated calcium modulator ORAI1. Expression tightly regulated during ontogeny: absent on hematopoietic stem cells and early pro-B, appears at late pro-B stage after productive immunoglobulin heavy chain rearrangement, persists through mat

Ref: NCBI Gene MS4A1 CD20 tetra-span; Janeway Immunobiology CD20 calcium channel rituximab ADCC CDC.

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Basic Applied Biology

Rituximab targets antigen:

Rituximab represents first chimeric anti-cancer monoclonal antibody approved 1997 targeting CD20, a 33 to 37 kDa non-glycosylated tetra-span membrane phosphoprotein encoded by MS4A1 gene on chromosome 11q12 expressed on pre-B through mature B lymphocytes but absent on hematopoietic stem cells, pro-B cells and terminally differentiated plasma cells. Protein architecture comprises four transmembrane domains with short intracellular termini and two extracellular loops accessible for antibody binding. Physiologic function involves regulation of calcium flux through modulating B cell receptor signa

Ref: Maloney et al. Blood 1997 Rituximab ideal target; Reff et al. CD20 biology; PubMed review CD20 therapeutic target.

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Flow cytometry, FACS, ELISA

What happens to radioactive signal in RIA if antigen is high?

Radioimmunoassay principle involves fixed limited antibody, fixed trace amount of radiolabeled antigen, and variable unlabeled antigen from sample competing for binding. At equilibrium, higher concentration of unlabeled antigen occupies more antibody sites, displacing labeled antigen into free fraction that is washed away. Radioactivity measured in bound pellet therefore decreases as sample antigen increases. This inverse relationship allows construction of standard curve. No change or direct proportionality would violate competition kinetics, equal distribution would indicate no affinity. Bou

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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