Which of the following features is not shared between `T cells' and '13 cells' -

Ans. is 'a' i.e., Positive Selection During Development . During development T cells undergo both positive selection and negative selection while B cells undergo only negative selection. B cell Development T cell Development (Negative Selection) (Positive selection followed by Negative Selection) . The immature B cells expressing membrane . T cells are selected for survival much more rigrously since IgM do not proliferate and differentiate in they should be able to recognize 'self' MHC molecules, but response to antigens. should not recognize 'self' peptides. . Their encounter with antigens (which are . Initially immature T cells that recognize MHC molecules aer usually 'self' as only 'self' antigens are selected and saved from programmed cell death. This is called presents at that time) in the bone marrow positive selection and ensures that T cells only recognize leads to death (apoptosis) or functional antigens in association with MHC. (This is impoant since irresponsiveness. T cells need to identify and react with (infected) host cells (Self) This propey is called Negative selection . Next, amongst positively selected Immature T cells, those of immature B cells and leads to T cells that react strongly with 'self peptides'; on MHC elemination (or clonal deletion) molecules undergo Neagtive selection (like B cells) and of immature B cells specific for apoptotic death, leading to elemination of immature T cells self antigens in the bone marrow specific for self antigens (peptides). This second step is called . B cells Negative Selection occurs in the Negative selection. bone marrow. . T cells positive & Negative selection occurs in Thymus. About other options . Class I MHC is expressed on both T cells and B cells. . Antigen specific receptors are found in both B cells (BCR : B cell receptors) and T cells (TCR: T cell receptors).