Homotypic cell aggregation via conformational change of CD44 molecule induced by anti-CD44 monoclonal antibodies

L. Cao, Tadashi Yoshino, R. Nishiuchi, I. Yamadori, T. Akagi

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Abstract

The homotypic cell aggregation of leukocytes is an unique adhesive event which is caused by cellular activation. Anti-CD44 monoclonal antibody (mAb) induces homotypic cell aggregation of hematopoietic cell lines expressing CD44, but the mechanism of homotypic cell aggregation is poorly understood. We used four mAbs against CD44: TL-1 which was newly developed and seemed to react with a non-hyaluronate binding site, OS/37 and BU52 which recognized a hyaluronate binding site, and Hermes-3 which recognized a non-hyaluronate binding site. TL-1 treatment induced strong homotypic cell aggregation in several types of cell lines including a B cell line from a patient with leukocyte adhesion deficiency syndromes (LAD) and normal peripheral blood lymphocytes (PBL). OS/37 and BU52 also induced weak homotypic cell aggregation. None of these anti-CD44 mAbs-induced homotypic cell aggregations was blocked by antibodies against LFA-1, ICAM-1, VLA-4, or L-selectin. Interestingly, the TL-1-induced homotypic cell aggregation was blocked by Hermes-3 or OS/37, but not by BU52. BU52-induced homotypic cell aggregation was blocked by Hermes-3 or OS/37, but not by TL-1. OS/37-induced homotypic cell aggregation was blocked by Hermes-3, TL-1 or BU52. The blocking experiments with anti-metabolic agents revealed that the induced homotypic cell aggregation was energy-dependent and associated with intracytoplasmic actin filaments. This homotypic cell aggregation did not require de novo protein synthesis, because it was not affected by pretreatment with either cycloheximide or actinomycin D. FACS analysis revealed that TL-1 binding did not affect the intensity of expression of the CD44 molecule on the cell surface. These findings suggest that anti-CD44 mAbs induce homotypic cell aggregation by causing a conformational change in the CD44 molecule. The cell activation pathway inducing the homotypic cell aggregation may be associated with several sites on the CD44 molecule, at least the hyaluronate binding site, Hermes-3 binding site, and TL-1 site. Taken together, multiple receptors on the CD44 molecule may have an advantage for immediate response to natural ligands, and activation of the CD44 molecule via a multivalent site may be related to leukocyte-binding to the HEV or migration into the stromal tissues.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalImmunobiology
Volume193
Issue number1
Publication statusPublished - 1995

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Cell Aggregation
Monoclonal Antibodies
Binding Sites
Cell Line
Leukocyte-Adhesion Deficiency Syndrome
Leukocytes
Integrin alpha4beta1
L-Selectin
Lymphocyte Function-Associated Antigen-1
Dactinomycin
Intercellular Adhesion Molecule-1
Cycloheximide
TL 1
Actin Cytoskeleton
Adhesives

ASJC Scopus subject areas

  • Immunology

Cite this

Homotypic cell aggregation via conformational change of CD44 molecule induced by anti-CD44 monoclonal antibodies. / Cao, L.; Yoshino, Tadashi; Nishiuchi, R.; Yamadori, I.; Akagi, T.

In: Immunobiology, Vol. 193, No. 1, 1995, p. 1-14.

Research output: Contribution to journalArticle

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AU - Akagi, T.

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N2 - The homotypic cell aggregation of leukocytes is an unique adhesive event which is caused by cellular activation. Anti-CD44 monoclonal antibody (mAb) induces homotypic cell aggregation of hematopoietic cell lines expressing CD44, but the mechanism of homotypic cell aggregation is poorly understood. We used four mAbs against CD44: TL-1 which was newly developed and seemed to react with a non-hyaluronate binding site, OS/37 and BU52 which recognized a hyaluronate binding site, and Hermes-3 which recognized a non-hyaluronate binding site. TL-1 treatment induced strong homotypic cell aggregation in several types of cell lines including a B cell line from a patient with leukocyte adhesion deficiency syndromes (LAD) and normal peripheral blood lymphocytes (PBL). OS/37 and BU52 also induced weak homotypic cell aggregation. None of these anti-CD44 mAbs-induced homotypic cell aggregations was blocked by antibodies against LFA-1, ICAM-1, VLA-4, or L-selectin. Interestingly, the TL-1-induced homotypic cell aggregation was blocked by Hermes-3 or OS/37, but not by BU52. BU52-induced homotypic cell aggregation was blocked by Hermes-3 or OS/37, but not by TL-1. OS/37-induced homotypic cell aggregation was blocked by Hermes-3, TL-1 or BU52. The blocking experiments with anti-metabolic agents revealed that the induced homotypic cell aggregation was energy-dependent and associated with intracytoplasmic actin filaments. This homotypic cell aggregation did not require de novo protein synthesis, because it was not affected by pretreatment with either cycloheximide or actinomycin D. FACS analysis revealed that TL-1 binding did not affect the intensity of expression of the CD44 molecule on the cell surface. These findings suggest that anti-CD44 mAbs induce homotypic cell aggregation by causing a conformational change in the CD44 molecule. The cell activation pathway inducing the homotypic cell aggregation may be associated with several sites on the CD44 molecule, at least the hyaluronate binding site, Hermes-3 binding site, and TL-1 site. Taken together, multiple receptors on the CD44 molecule may have an advantage for immediate response to natural ligands, and activation of the CD44 molecule via a multivalent site may be related to leukocyte-binding to the HEV or migration into the stromal tissues.

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