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→Lymphocyte Surveillance
<p>If a naive lymphocyte recognises an antigen then it differentiates into its adult (mature) form. [[T cell differentiation#Dendritic Cells|Interdigitating dendritic cells]] present antigen to T cells and [[B cell differentiation#Follicular Dendritic Cells|follicular dendritic cells]] present antigen to B cells.</p>
<p>If a naive lymphocyte recognises an antigen then it differentiates into its adult (mature) form. [[T cell differentiation#Dendritic Cells|Interdigitating dendritic cells]] present antigen to T cells and [[B cell differentiation#Follicular Dendritic Cells|follicular dendritic cells]] present antigen to B cells.</p>
<p>B cells proliferate into [[B cell differentiation#Plasma cells|plasma cells]] within sectors of the lymph nodes known as germinal centres, producing antibody.</p>
<p>B cells proliferate into [[B cell differentiation#Plasma cells|plasma cells]] within sectors of the lymph nodes known as germinal centres, producing antibody.</p>
<p>T cells leave the lymph node in '''attack mode''' to locate the infectious organism. The surface molecule L-selectin (which allows the naive lymphocyte to enter the lymph node via an [[Lymph Nodes - Anatomy & Physiology#High endothelial venules|HEV]]) is replaced by the adhesion molecule VLA-4. At the site of inflammation, the VLA-4 receptor recognises VCAM-1 on endothelial cells and the T cell enters the site of disease. [[T cells|CD4+ T cells]] search for infected macrophages and [[T_cells#Cytotoxic_CD8.2B|CD8+ T cells]] look for virus infected cells creating an immune response. After the infection has been defeated, memory cells develop which express L-selectin (rather than VLA-4) and continue to search the body in surveillance mode in case the host is re-infected with the disease producing organism.
<p>T cells leave the lymph node in '''attack mode''' to locate the infectious organism. The surface molecule L-selectin (which allows the naive lymphocyte to enter the lymph node via an [[Lymph Nodes - Anatomy & Physiology#High endothelial venules|HEV]]) is replaced by the adhesion molecule VLA-4. At the site of inflammation, the VLA-4 receptor recognises VCAM-1 on endothelial cells and the T cell enters the site of disease. [[T cells|CD4<sup>+</sup> T cells]] search for infected macrophages and [[T_cells#Cytotoxic_CD8.2B|CD8<sup>+</sup> T cells]] look for virus infected cells creating an immune response. After the infection has been defeated, memory cells develop which express L-selectin (rather than VLA-4) and continue to search the body in surveillance mode in case the host is re-infected with the disease producing organism.