Innate vs. Adaptive Immunity

  Innate immunity Adaptive immunity
COMPONENTS Neutrophils, macrophages, monocytes, dendritic cells, mast cells, eosinophils, basophils, natural killer (NK) cells (lymphoid origin), complement, physical epithelial barriers, secreted enzymes. T cells, B cells, circulating antibodies
MECHANISM Germline encoded Variation through V(D)J recombination during lymphocyte development in the bone marrow
RESISTANCE Resistance persists through generations; does not change within an organism’s lifetime Microbial resistance not heritable

Occurs rapidly (minutes to hours)

No memory response

Highly specific, refined over time Develops over long periods; memory response is faster and more robust
SECRETED PROTEINS Lysozyme, complement, C-reactive protein (CRP), defensins Immunoglobulins
KEY FEATURES IN PATHOGEN RECOGNITION Toll-like receptors (TLRs) on macrophages and dendritic cells: pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs) and lead to activation of the transcription factor NF-κB → activates immune response genes → immune mediators.

Examples of PAMPs include LPS (on  outer membrane of gram ⊝ bacteria) recognition by CD14 on macrophages, flagellin (bacteria), nucleic acids (viruses). Dectin-1 pattern recognition receptors on phagocytes detect fungi.

Memory cells: activated B and T cells; subsequent exposure to a previously encountered antigen → stronger, quicker immune response

TLRs are also present.


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