Studies On Mechanisms Of The Phenomenon Of Lupus Band In Systemic Lupus Erythematosus Patients

Lupus band test (LET) is one of the important assistant methods in diagnosing systemic lupus erythematosus (SLE), but the mechanisms of it's formation is still unknown. It is well known that lupus band results from the deposition of immunocomplex. It is unclear the immunocomplex depositing at basement membrane zone (BMZ) is from blood circulation or is composed of circulating antibodies and BMZ autoantigiens in situ. Recent studies show thatthere are cutaneous basement membrane zone autoantibodies (BMZ-Ab) in seraof SLE patients. But it remains ambiguous if there are BMZ-Ab or otherautoantigens and antibodies in lupus band. This study was investigated to detectif BMZ-Ab and if DNA participate in the formation of lupus band in SLE.Immunofluorescence (IF), immunoblotting (IB) and gold-labeled indirectimmunoelectron microscope (gold-IIEM) techniques were utilized to localizeantigen recognized by BMZ-Ab and anti-dsDNA antibodies in 15 SLE cases (LBT are positive in 10 cases and negative in 5 cases). Direct immunofluorescence (DIF) staining showed that 9/10 cases of specimens hadfluorescence on epidermal or dermal side of salt-split skin. Indirectimmunofluorescence (IIF) staining revealed that 14/15 (93.3%) cases of SLE serashowed fluorescence along the roof of epidermal of salt-split skin. By IB analysis,all the 15 SLE sera have several kinds of IgG and/or IgA type autoantibodies which reacted with epidermal and/or dermal extracts., such as 230kD. 200kD, 180kD, 130kD, 97kD epidermal extracts and 180kD, 160kD, 130kD, 116kD, 97kD dermal antigens. By gold-DIEM and HEM analysis, gold particlesdeposited at about the same area of BMZ. Gold particles directed to every region of BMZ of either SLE patients skin or normal human skin. It got the same resultthat anti-dsDNA antibodies reacted with skin of both SLE patients and normal human. IF staining showed no fluorescence along BMZ, but revealed pemphigus-like plasmalemma hypofluorescence besides perinuclear stain of keratinocytes. By IBM analysis, a few gold particles deposited at basal plasmalemma of BMZ. By IB analysis, anti-dsDNA antibodies showed reactivity with neither epidermal nor dermal antigens.This study further comfirms the existence of BMZ-Ab in SLE sera. These antibodies show obvious heterogeneity for their reaction with many kinds of dermal or epidermal antigens. The tissue-binding deposion of BMZ-Ab is identical with that of immunocomplex in lupus band, which suggests BMZ-Ab participate in the formation of lupus band. We didn't detect any positive reactions along dermoepidermal junction using nti-dsDNA antibody reacted with skin of SLE patients, but found a weak reaction on plasmalemma of keratinocytes whether use SLE skin or normal human skin as substrates. These results hint that dsDNA or the immunocomplex of dsDNA and anti-dsDNA antibodies might not take part in the formation of lupus band and there may be a cross-reaction between anti-dsDNA antibody and plamalemma of keratinocytes.