Changes

[[Lymphocytes#T Cells|T cell]] receptors ('''TCR''') recognise '''antigen fragments''' (that is digestion products) on the '''surface of cells''', whereas [[Lymphocytes#B Cells|B cell]] receptors ('''BCR''') bind '''whole antigen''' in the '''extracellular fluid'''.  [[Lymphocytes#T Cells|T cells]] only "see" antigen when it is presented by [[Major Histocompatability Complexes|'''MHC''']] (Major Histocompatibility Complex) on the cell surface.  Antigen digestion and presentation is one of the major functions of the [[T cell differentiation#Antigen Presentation by Dendritic Cells|'''dendritic cells''']] (circulating [[Monocytes|monocytes]]) and '''[[Macrophages|macrophages]]'''.  These are referred to as '''Antigen-Presenting Cells''' (APCs).   

[[Lymphocytes#T Cells|T cell]] receptors ('''TCR''') recognise '''antigen fragments''' (that is digestion products) on the '''surface of cells''', whereas [[Lymphocytes#B Cells|B cell]] receptors ('''BCR''') bind '''whole antigen''' in the '''extracellular fluid'''.  [[Lymphocytes#T Cells|T cells]] only "see" antigen when it is presented by [[Major Histocompatability Complexes|'''MHC''']] (Major Histocompatibility Complex) on the cell surface.  Antigen digestion and presentation is one of the major functions of the [[T cell differentiation#Antigen Presentation by Dendritic Cells|'''dendritic cells''']] (circulating [[Monocytes|monocytes]]) and '''[[Macrophages|macrophages]]'''.  These are referred to as '''Antigen-Presenting Cells''' (APCs).   

Naive B-cells express [[Immunoglobulin D|IgD]] and [[Immunoglobulin M|IgM]] on their cell surfaces, which bind antigen as it is washed into lymph tissue with the afferent lymph fluid.  Antigen is presented to [[Lymphocytes#B Cells|B cells]] by [[B cell differentiation#Antigen Presentation by Follicular Dendritic Cells|'''follicular dendritic cells''' (FDCs)]], which are also classed as APCs.  [[B cell differentiation#Antigen Presentation by Follicular Dendritic Cells|FDCs]] can endocytose antigen directly from the afferent lymph or receive them from [[Lymphocytes#Helper CD4+|CD4+ T-cells]].

Naive B-cells express [[Immunoglobulin D|IgD]] and [[Immunoglobulin M|IgM]] on their cell surfaces, which bind antigen as it is washed into lymph tissue with the afferent lymph fluid.  Antigen is presented to [[Lymphocytes#B Cells|B cells]] by [[B cell differentiation#Antigen Presentation by Follicular Dendritic Cells|'''follicular dendritic cells''' (FDCs)]], which are also classed as APCs.  [[B cell differentiation#Antigen Presentation by Follicular Dendritic Cells|FDCs]] can endocytose antigen directly from the afferent lymph or receive them from [[Lymphocytes#Helper CD4+|CD4⁺ T-cells]].

===Cellular response: Proliferation and Differentiation===

===Cellular response: Proliferation and Differentiation===