TY  - CHAP
M1  - Book, Section
TI  - Antibody Deficiencies
A1  - Conley, Mary Ellen
A2  - Valle, David L.
A2  - Antonarakis, Stylianos
A2  - Ballabio, Andrea
A2  - Beaudet, Arthur L.
A2  - Mitchell, Grant A.
PY  - 2019
T2  - The Online Metabolic and Molecular Bases of Inherited Disease
AB  - Antibody  deficiencies  are  a  heterogeneous  group  of  disorders  characterized  by  recurrent  bacterial  infections.  Otitis,  sinusitis,  and  pneumonia  owing  to  the  encapsulated  organisms  Streptococcus  pneumoniae  or  Haemophilus  influenzae  are  the  most  common  infections.  However,  more  severe  infections,  such  as  sepsis,  meningitis,  cellulitis,  and  osteomyelitis,  are  not  unusual.  An  antibody  deficiency  may  occur  as  an  isolated  finding,  or  it  may  be  part  of  a  multisystemic  disease  that  affects  other  limbs  of  the  immune  system  or  other  organ  systems.  Treatment  consists  of  antibody  replacement  and  aggressive  use  of  antibiotics.Antibodies  are  a  highly  diverse  family  of  serum  glycoproteins  that  bind  to  and  help  remove  invading  microorganisms,  extraneous  proteins,  or  foreign  cells.  Collectively,  they  account  for  over  a  third  of  the  protein  found  in  serum.  The  typical  antibody  molecule  is  made  up  of  two  immunoglobulin  (Ig)  heavy  chains  and  two  light  chains.  There  are  five  major  classes  of  immunoglobulins  or  antibodies:  IgM,  IgG,  IgA,  IgE,  and  IgD.  The  IgG  class  can  be  further  divided  into  four  subclasses  (IgG1,  IgG2,  IgG3,  and  IgG4),  and  IgA  can  be  divided  into  two  subclasses  (IgA1  and  IgA2).  The  class  of  the  immunoglobulin  is  defined  on  the  basis  of  the  type  of  heavy  chain.  There  are  two  families  of  light  chains,  κ  and  λ,  each  of  which  can  function  with  any  class  of  heavy  chain.The  immunoglobulin  heavy-chain  genes  are  located  at  the  telomere  of  chromosome  14q32.3.  The  κ  family  is  at  2p12,  and  the  λ  family  is  encoded  at  22q11.  At  each  of  these  three  locations,  there  are  three  or  four  families  of  gene  segments:  the  variable  (V)  region,  the  diversity  (D)  region,  the  joining  (J)  region,  and  the  constant  (C)  region;  these  gene  segments  can  be  assembled  in  a  myriad  of  ways  to  create  a  highly  diverse  repertoire  of  antibodies.  Additional  variation  is  introduced  by  the  fact  that  each  heavy  chain  may  be  associated  with  many  different  light  chains.Antibodies  are  produced  by  plasma  cells,  the  terminally  differentiated  descendants  of  the  B-cell  lineage.  The  early  stages  of  B-cell  development  occur  in  the  bone  marrow,  where  pro-B  cells,  which  are  derived  from  hematopoietic  stem  cells,  undergo  rearrangement  of  the  immunoglobulin  heavy-chain  genes.  This  process  occurs  throughout  the  life  of  the  individual.  At  the  next  stage  of  B-cell  differentiation,  in  pre-B  cells,  there  is  rearrangement  of  the  light-chain  genes.  This  allows  the  expression  of  the  intact  immunoglobulin  molecule  on  the  cell  surface  of  the  B  cell.  Each  B  cell  and  its  progeny  express  only  one  rearranged  immunoglobulin  heavy  chain  and  one  light  chain.  When  antigen  binds  to  the  surface  of  the  B  cell,  if  the  appropriate  environmental  signals  are  received,  the  B  cell  proliferates  and  differentiates  into  a  memory  B  cell  that  can  respond  more  rapidly  to  future  exposures  to  that  antigen  or  to  a  plasma  cell  that  secretes  high  concentrations  of  antibodies.Defects  in  early  B-cell  development  are  associated  with  the  onset  of  infections  in  the  first  few  years  of  life,  profound  hypogammaglobulinemia,  and  an  absence  of  B  cells  in  the  peripheral  circulation.  Between  80  and  90  percent  of  patients  with  this  disorder  have  ...
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/16
UR  - ommbid.mhmedical.com/content.aspx?aid=1181457793
ER  -