Claim: Lymph nodes are major sites of B lymphocytes that plays a central role in cell-mediated immunity.

The adaptive immune system , also known as the acquired immune system or , more rarely , as the specific immune system , is a subsystem of the overall immune system that is composed of highly specialized , systemic cells and processes that eliminate pathogens or prevent their growth . The adaptive immune system is one of the two main immunity strategies found in vertebrates -LRB- the other being the innate immune system -RRB- . Adaptive immunity creates immunological memory after an initial response to a specific pathogen , and leads to an enhanced response to subsequent encounters with that pathogen . This process of acquired immunity is the basis of vaccination . Like the innate system , the adaptive system includes both humoral immunity components and cell-mediated immunity components .   Unlike the innate immune system , the adaptive immune system is highly specific to a particular pathogen . Adaptive immunity can also provide long-lasting protection ; for example , someone who recovers from measles is now protected against measles for their lifetime . In other cases it does not provide lifetime protection ; for example , chickenpox . The adaptive system response destroys invading pathogens and any toxic molecules they produce . Sometimes the adaptive system is unable to distinguish harmful from harmless foreign molecules ; the effects of this may be hayfever , asthma or any other allergy . Antigens are any substances that elicit the adaptive immune response . The cells that carry out the adaptive immune response are white blood cells known as lymphocytes . Two main broad classes -- antibody responses and cell mediated immune response -- are also carried by two different lymphocytes -LRB- B cells and T cells -RRB- . In antibody responses , B cells are activated to secrete antibodies , which are proteins also known as immunoglobulins . Antibodies travel through the bloodstream and bind to the foreign antigen causing it to inactivate , which does not allow the antigen to bind to the host .   In acquired immunity , pathogen-specific receptors are `` acquired '' during the lifetime of the organism -LRB- whereas in innate immunity pathogen-specific receptors are already encoded in the germline -RRB- . The acquired response is called `` adaptive '' because it prepares the body 's immune system for future challenges -LRB- though it can actually also be maladaptive when it results in autoimmunity -RRB- .   The system is highly adaptable because of somatic hypermutation -LRB- a process of accelerated somatic mutations -RRB- , and V -LRB- D -RRB- J recombination -LRB- an irreversible genetic recombination of antigen receptor gene segments -RRB- . This mechanism allows a small number of genes to generate a vast number of different antigen receptors , which are then uniquely expressed on each individual lymphocyte . Since the gene rearrangement leads to an irreversible change in the DNA of each cell , all progeny -LRB- offspring -RRB- of that cell inherit genes that encode the same receptor specificity , including the memory B cells and memory T cells that are the keys to long-lived specific immunity .   A theoretical framework explaining the workings of the adaptive immune system is provided by immune network theory . This theory , which builds on established concepts of clonal selection , is being applied in the search for an HIV vaccine .