In a large pool of B lymphocytes, each is specific for one antigen. B1 B2 ВЗ B4 *Antigens When an antigen binds to a B cell, the B cell divides. B2 Primary immune Clone of B cells response 3.and gives rise to a clone of B cells, all specific for the same antigen. B2 B2 B2 82 B2 B2 This proliferation of lymphocytes is the primary immune response. Plasma cells Some cells differentiate into antibody-secreting plasma cells. 6 Antibodies are specific for the antigen. Antibodies Secondary immune Memory B2 cells Memory cells remain in circulation. B2 response 8 if the same antigen reappears at a later time,. Antigen 9.the antigen binds to the B2 memory cells,.. Secondary immune Memory B2 cells Memory cells remain in circulation. B2 response B f the same antigen reappears at a later time,. Antigen the antigen binds to the B2 memory cells. B2 B2 B2 B2 82 B2 10.which rapidly give rise to a secondary immune response. Plasma cells Memory cells Antibodies 22.21 An immune response to a specific antigen is produced through clonal selection.

A gene, which we will call gene C, can be epigenetically modified in such a way that its expression in some cells is permanently silenced. Describe how you could conduct cell-fusion experiments to determine if a cis- or a trans-epigenetic mechanism is responsible for maintaining the silencing of gene C.

Imatinib is an anti-cancer drug that inhibits the function of CD117, a receptor protein coded for by the KIT gene. Mutations in the KIT gene are implicated in gastrointestinal cancers.  Aimee, who has a gastrointestinal tumor asked her doctor if she could try Imatinib, but her doctor first required that she get a biopsy of her tumor. Hair loss is a well-known side effect of chemotherapy; why does this side effect occur? (1) Chemotherapy targets cells undergoing division. Hair stem cells are constantly replenishing (growing) just like cancer cells. They are then also targeted by chemotherapy, causing hair loss. (2) Chemotherapy targets all cells, whether dividing or not dividing, and hair cells are collateral in the fight against cancer (3) Chemotherapy targets proteins in our cells and hair cells have an abundance of proteins

A C-terminal KDEL tetrapeptide was identified by “sequence gazing” as a possiblesignal for keeping resident ER proteins in the ER. This idea is now described in yourtextbook as established fact. What types of experiments do you think were performedto confirm that KDEL serves as an ER localization signal?