The first line of defense against non-self pathogens is the innate, or non-specific, immune response. The innate immune response consists of physical, chemical and cellular defenses against pathogens. The main purpose of the innate immune response is to immediately prevent the spread and movement of foreign pathogens throughout the body.
The second line of defense against non-self pathogens is called adaptive immune response. Adaptive immunity is also referred to as acquired immunity or specific immunity and is only found in vertebrates. The adaptive immune response is specific to the pathogen presented. The adaptive immune response is meant to attack non-self pathogens but can sometimes make errors and attack itself. When this happens, autoimmune diseases can develop (e.g., lupus, rheumatoid arthritis).
The hallmark of the adaptive immune system is clonal expansion of lymphocytes. Clonal expansion is the rapid increase of T and B lymphocytes from one or a few cells to millions. Each clone that originates from the original T or B lymphocyte has the same antigen receptor as the original and fights the same pathogen.
While the innate immune response is immediate, the adaptive immune response is not. However, the effect of the adaptive immune response is long-lasting, highly specific, and is sustained long-term by memory T cells.
|
Line of Defense |
Timeline |
Cells |
Antigen Dependency |
Examples |
Innate
(non-specific) |
First |
Immediate response (0 -96 hours) |
Natural killer cells, macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils |
Independent |
Skin, hair, cough, mucous membranes, phagocytes, granulocytes |
Adaptive
(specific) |
Second |
Long term (>96 hours) |
T and B lymphocytes |
Dependent |
Pus, swelling, redness, pain, T and B lymphocyte response |
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