RT Book, Section
A1 Jameson, J. Larry
A1 Fauci, Anthony S.
A1 Kasper, Dennis L.
A1 Hauser, Stephen L.
A1 Longo, Dan L.
A1 Loscalzo, Joseph
SR Print(0)
ID 1167063333
T1 Lymphadenopathy and Splenomegaly
T2 Harrison's Manual of Medicine, 20e
YR 2020
FD 2020
PB McGraw-Hill Education
PP New York, NY
SN 9781260455342
LK accessmedicine.mhmedical.com/content.aspx?aid=1167063333
RD 2023/05/30
AB Exposure  to  antigen  through  a  break  in  the  skin  or  mucosa  results  in  antigen  being  taken  up  by  an  antigen-presenting  cell  and  carried  via  lymphatic  channels  to  the  nearest  lymph  node.  Lymph  channels  course  throughout  the  body  except  for  the  brain  and  the  bones.  Lymph  enters  the  node  through  the  afferent  vessel  and  leaves  through  an  efferent  vessel.  Because  antigen-presenting  cells  pass  through  lymph  nodes,  they  present  antigen  to  lymphocytes  residing  there.  Lymphocytes  in  a  node  are  constantly  being  replaced  by  antigen-naïve  lymphocytes  from  the  blood.  They  are  retained  in  the  node  via  special  homing  receptors.  B  cells  populate  the  lymphoid  follicles  in  the  cortex;  T  cells  populate  the  paracortical  regions.  When  a  B  cell  encounters  an  antigen  to  which  its  surface  immunoglobulin  can  bind,  it  stays  in  the  follicle  for  a  few  days  and  forms  a  germinal  center  where  the  immunoglobulin  gene  is  mutated  in  an  effort  to  make  an  antibody  with  higher  affinity  for  the  antigen.  The  B  cell  then  migrates  to  the  medullary  region,  differentiates  into  a  plasma  cell,  and  secretes  immunoglobulin  into  the  efferent  lymph.