Title : Cleavage of Langerhans cell surface
CD1a molecule by trypsin
Abstract :
- The T-cell surface differentiation antigens expressed on cortical thymocytes are composed of 3 molecules, CD1a (Mr 49,000), CD1b (Mr 45,000), and CD1c (Mr 43,000), which are non-covalently attached to beta 2-microglobulin
- In the present study, differences in quantitative binding (immunogold labelling) were observed with four CD1a monoclonal antibodies (mAb), Na1/34, L544, Vit6 and OKT6, on epidermal Langerhans cells obtained through trypsinization and Ficoll-Hypaque sedimentation
- These cells were surface-labelled with 125I and then lysed
- Immunoprecipitation was carried out with five CD1a mAb, BL6, 10D12.2, L404, L544 and OKT6, and immunoprecipitates were electrophoretically run
- All CD1a mAb except OKT6 immunoprecipitated an additional molecule with an apparent relative mass of 27,000 , under reducing conditions
- CD1a antigen (Mr 49,000) was borne by the same chain of Mr 49,000 on cortical thymocytes and Langerhans cells, whereas the Mr 27,000 molecule was never found on thymic cells
- On two-dimensional gel analysis, the Mr 27,000 molecule showed a pattern with 3 major spots with pI of 5.6, 5.9 and 6.2
- This Mr 27,000 protein was found to contain one N-linked oligosaccharide residue by endoglycosidase-F treatment
- By sequential immunoprecipitation, this Mr 27,000 molecule was shown to be different from the major histocompatibility complex class II beta-chains (DR, DP)
- As the Mr 27,000 molecule was not precipitated with OKT6, sequential immunoprecipitation confirmed specific recognition of this low molecular weight protein by other CD1a mAb
- The protein of apparent molecular mass 27,000 was considered to be a breakdown product of Mr 49,000 ( CD1a ) antigen
- These results suggested that the CD1a molecule was sensitive to trypsin