In clonal selection of B cells, which substance is responsible for determining which cells will eventually become cloned?

A. Antibody:Antibodies are produced by B cells after activation and clonal expansion. They do not determine which B cells will be selected; instead, they are the end product of the immune response.

B. Interferon:Interferons are signaling proteins that help modulate the immune response, particularly against viral infections. They do not directly influence the selection of B cells for clonal expansion.

C. Complement:The complement system enhances pathogen destruction and inflammation but does not select specific B cells for cloning. Its role is part of innate immunity, not clonal selection.

D. Antigen:Antigens bind to specific B cell receptors, selecting which B cells will proliferate. Only B cells whose receptors recognize the antigen undergo clonal expansion, differentiating into plasma cells and memory B cells, which ensures a targeted adaptive immune response.

A. Inflammation:Inflammation is part of the second line of defense, an innate immune response that occurs after pathogens bypass physical barriers. It involves leukocyte recruitment and vascular changes to fight infection.

B. Mucous membranes:Mucous membranes form a physical and chemical barrier that traps pathogens and prevents their entry into the body. They are a key component of the first line of defense, along with skin and secretions like saliva and tears.

C. Natural killer cells:Natural killer cells are part of the innate immune system’s second line of defense. They identify and destroy infected or abnormal cells but act after pathogens have entered the body.

D. Phagocytes:Phagocytes, such as neutrophils and macrophages, are part of the second line of defense. They engulf and destroy pathogens that have breached the first line of defense barriers.