Pattern Recognition Receptor (PRR)

Pathogen-Associated Molecular Patterns (PAMPs)

Damage-associated molecular patterns (DAMPs)

Skin and mucous membranes and their accessory components (the first line of defense against mechanical pathogens)

body barrier

complement system

acute response phase protein

Antimicrobial peptides and lysozyme

Cytokines

After 96 hours, immature DC cells migrate to peripheral immune organs, gradually differentiate into mature DC, and present pMHC complexes to T cells.

Within 4 hours, neutrophils are the main effector cells against fungi and bacteria, and most bacterial infections end during this period

4-96 hours

Second signal of T cell activation

The first signal of T cell activation

Cytokines involved in T cell activation

Proliferation and differentiation of CD4⁺T cells, proliferation and differentiation of CD8⁺T cells

Endogenous antigens are processed in nucleated cells, degraded by the proteasome and entered into the endoplasmic reticulum (ER), where they bind to MHC class I molecules and are presented to CD8⁺T cells for recognition. Some exogenous antigens can also be processed according to the endogenous presentation pathway

Exogenous antigens are taken up by APC, fuse with lysosomes to form endosomes/lysosomes, and combine with MHC class II molecules for recognition by CD4⁺T cells.

MHC molecules cross-present antigens CD1, molecular presentation pathway (certain lipid antigens)

Effect-target cell binding and polarization

CTL specifically kills target cells

Treg: effector T cell immune incompetence Tfh: Promote B cell proliferation and differentiation and antibody formation Th17: activates neutrophils and triggers local inflammatory response Th22 is involved in autoimmune diseases

Th2 auxiliary humoral immune response and other effects

Th1-mediated delayed-type hypersensitivity

The first signal of B cell activation

The role of cytokines

Second signal of B cell activation

Proliferation and differentiation of antigen-specific B cells

The fate of B cells in germinal centers

B cell proliferation and differentiation in germinal centers

Incubation period, logarithmic phase, plateau phase, decline phase Mainly produces IgM class antibodies The total amount of antibodies and their affinity to the antigen are low

Low antigen dosage can effectively initiate immune response again Memory B cells act as APCs to ingest and process antigens and present antigen peptides to memory Th cells. The response is rapid and durable, the response intensity is high, the antibody type is mainly IgG, and the antibody affinity produced is significantly higher than the initial response.

Innate, stable inheritance Able to distinguish "self" from "non-self", limited specificity No typical immune memory Quickly exert immune effect

Produced after exposure to pathogens Highly specific Immune effects have a latency period Have immune memory and can form immune tolerance