PATHOLOGY

Detailed explanation-1: -And a similar increase in memory killer T cells prevents severe disease and hospitalization. Memory cells can remain in the immune system for long periods – sometimes even up to 75 years.

Detailed explanation-2: -Memory B cells can survive for decades, which gives them the capacity to respond to multiple exposures to the same antigen. The long-lasting survival is hypothesized to be a result of certain anti-apoptosis genes that are more highly expressed in memory B cells than other subsets of B cells.

Detailed explanation-3: -The adaptive, or acquired, immune response takes days or even weeks to become established-much longer than the innate response; however, adaptive immunity is more specific to pathogens and has memory.

Detailed explanation-4: -Memory cells persist after a primary exposure to a pathogen. If re-exposure occurs, memory cells differentiate into effector cells without input from the innate immune system.