JL1, a novel differentiation antigen of human cortical thymocyte.

Abstract

SummaryExpression of a novel thymocyte differentiation antigen, JL1, defined by a monodonal antibody (mAb) developed against human thymocytes showed a specificity for stage II double positive (CD4+CD8 +) human cortical thymocytes. This antigen was not expressed at detectable levels on medullary thymocytes, mature peripheral leukocytes, bone marrow cells or on other types of tissues elsewhere in the human body. Immunohistologic analysis revealed that JL1 had a clear pattern of distribution on cortical thymocytes. Immunoprecipitation of 12SI-labded cell lysates from human thymocytes and Molt-4 leukemic cell line with anti-JL1 mAb yielded a 120-130-kD single chain glycoprotein. When immunoprecipitation of cell lysate was done after endoglycosidase F treatment, JL1 antigen was still detected by antibody but the band showed a reduction in apparent molecular mass of "~ kD. This suggests that, although JL1 molecule contains carbohydrate group, this does not form a critical part of the antigenic determinant for anti-JL1 antibody. JL1 antigen appears to be the first double positive, stage-specific differentiation antigen of human thymocyte reported so far. This antigen would be a useful marker for lymphoblastic malignancy of stage II thymocyte origin and it may be involved in the thyrnocyte education process.

Expression of Leukemia-Associated Antigen, JL1, in Bone Marrow and Thymus

“…These findings, together with the fact that JL1 is not expressed on mature peripheral monocytes or granulocytes, 17 suggest that JL1 antigen is expressed during the later maturation process in the case of myelomonocytic hematopoiesis. Taken together, these results showed that JL1 antigen is specifically expressed at the earlier stages of B and T cell lineages as well as at the later stage of myelomonocytic cells in BM but not on pluripotent stem cells or not on mature peripheral blood cells ( Figure 6).…”

“…Collectively, JL1 is likely to be firstly expressed from common lymphoid progenitors and widely distributed during lymphoid ontogenesis, and to be down-regulated at the time of the final maturation process because JL1 is not expressed on peripheral mature T or B cells. 17 These suggest a possible role of the down-regulation of JL1 molecule in the completion of lymphocyte maturation.…”

“…17,19 Biotinylation of anti-JL1 mAb was performed with biotin hydrazine (Pierce, Rockford, IL) according to the manufacturer's protocols. 20,21 The directly labeled mAbs were purchased as follows: lo cells were well visualized, because cychrome-conjugated streptavidin has excellent quantum efficiency.…”

A cell surface molecule, JL1; a specific target for diagnosis and treatment of leukemias

“…16 The ascitic form of anti-JL1 mAb was produced after injection of hybridoma cells into pristane-pretreated Balb/c mice. The antibody was purified using Qsepharose (Pharmacia) and hydroxylapatite (Bio-gel HTP gel; Pharmacia) column chromatography.…”

“…16 Briefly, the cells were surface-radiolabeled with 125 I using lactoperoxidase-catalyzed iodination, and were lysed in the buffer (50 mM Tris-HCl, pH 7.4, 50 mM EDTA, 1 mM PMSF) containing 1% (v/v) Nonidet P-40. After preclearing by mixing the lysate with irrelevant immunoglobulin-conjugated protein A-sepharose CL-4B beads, immunoprecipitations were done by mixing lysate with anti-JL1 mAb-conjugated protein A-sepharose CL-4B beads.…”