Abstract: Objective: To  explore  the  clinical  significance  of  monoclonal  light  chain  antibody  staining  in  renal tissue paraffin  sections. Methodology: The  clinical  and  pathological  data  of  autologous  renal  biopsy  performed  in  the National Clinical Research Center for Kidney  Disease  from January 2022 to  December 2023  were  analyzed.  Among 8 376 patients， 757 patients underwent  both  frozen  section  and  paraffin  section  light  chain  staining，  and  the  results  of  the  two kinds of  immunostaining  were  analyzed  and  compared. Results: Among  757  patients，  284  had  no  frozen  tissue  or  no glomeruli in the frozen  tissue.  The  light  chain  staining  results  of  450  cases  were  basically  consistent  between  frozen  and paraffin tissues. In 23 cases， the fluorescence staining results of monoclonal light chain antibodies on frozen sections could not clearly determine  whether  the  deposits  were  monoclonal，  whereas  the  fluorescence  staining  of  monoclonal  light  chain antibodies on paraffin sections could better distinguish the staining intensity of the two light chains， thereby  clarifying  the diagnosis of kidney diseases.  These  included 10  cases  of  proliferative  glomerulonephritis  with  monoclonal  immunoglobulin deposits， 8 cases of AL amyloidosis， 3 cases of myeloma cast nephropathy， and 2 cases of light chain proximal tubulopathy. Conclusion:This  paper  provides  the  first  comprehensive  analysis  of  the  quality  and  coping  strategies  for  light  chain staining， finding  that  monoclonal  light  chain  antibody  fluorescence  staining  on  paraffin  sections，  as  a  supplement  to fluorescence staining on frozen sections， has significant diagnostic value， especially for monoclonal immunoglobulin-related
kidney diseases.

Key words: light chain antibodies, light chain , renal tissue paraffin sections, immunofluorescence