RT Book, Section
A1 Fischer, Alain
A2 Jameson, J. Larry
A2 Fauci, Anthony S.
A2 Kasper, Dennis L.
A2 Hauser, Stephen L.
A2 Longo, Dan L.
A2 Loscalzo, Joseph
SR Print(0)
ID 1155952301
T1 Primary Immune Deficiency Diseases
T2 Harrison's Principles of Internal Medicine, 20e
YR 2018
FD 2018
PB McGraw-Hill Education
PP New York, NY
SN 9781259644016
LK accesspharmacy.mhmedical.com/content.aspx?aid=1155952301
RD 2024/04/20
AB Immunity  is  intrinsic  to  life  and  an  important  tool  in  the  fight  for  survival  against  pathogenic  microorganisms.  The  human  immune  system  can  be  divided  into  two  major  components:  the  innate  immune  system  and  the  adaptive  immune  system  (Chap.  342).  The  innate  immune  system  provides  the  rapid  triggering  of  inflammatory  responses  based  on  the  recognition  (at  the  cell  surface  or  within  cells)  of  either  molecules  expressed  by  microorganisms  or  molecules  that  serve  as  “danger  signals”  released  by  cells  under  attack.  These  receptor/ligand  interactions  trigger  signaling  events  that  ultimately  lead  to  inflammation.  Virtually  all  cell  lineages  (not  just  immune  cells)  are  involved  in  innate  immune  responses;  however,  myeloid  cells  (i.e.,  neutrophils  and  macrophages)  play  a  major  role  because  of  their  phagocytic  capacity.  The  adaptive  immune  system  operates  by  clonal  recognition  of  antigens  followed  by  a  dramatic  expansion  of  antigen-reactive  cells  and  execution  of  an  immune  effector  program.  Most  of  the  effector  cells  die  off  rapidly,  whereas  memory  cells  persist.  Although  both  T  and  B  lymphocytes  recognize  distinct  chemical  moieties  and  execute  distinct  adaptive  immune  responses,  the  latter  is  largely  dependent  on  the  former  in  generating  long-lived  humoral  immunity.  Adaptive  responses  utilize  components  of  the  innate  immune  system;  for  example,  the  antigen-presentation  capabilities  of  dendritic  cells  help  to  determine  the  type  of  effector  response.  Not  surprisingly,  immune  responses  are  controlled  by  a  series  of  regulatory  mechanisms.