-Author name in bold denotes the presenting author
-Asterisk * with author name denotes a Non-ASH member
Clinically Relevant Abstract denotes an abstract that is clinically relevant.

PhD Trainee denotes that this is a recommended PHD Trainee Session.

Ticketed Session denotes that this is a ticketed session.

2397 LFA-1-Mediated Adhesion to ICAM-2 Is Critical for Stromal Cell-Dependent Early T-Lymphoid Differentiation from Human Hematopoietic Precursors

Hematopoiesis and Stem Cells: Microenvironment, Cell Adhesion and Stromal Stem Cells
Program: Oral and Poster Abstracts
Session: 506. Hematopoiesis and Stem Cells: Microenvironment, Cell Adhesion and Stromal Stem Cells: Poster II
Sunday, December 6, 2015, 6:00 PM-8:00 PM
Hall A, Level 2 (Orange County Convention Center)

Hirohito Minami1*, Kohshi Ohishi, MD, PhD2, Masahiro Masuya, MD, PhD1 and Naoyuki Katayama, MD, PhD1

1Department of Hematology and Oncology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
2Blood Transfusion Service, Mie University Hospital, Tsu, Mie, Japan

The regulatory mechanism of human early T-lymphoid differentiation remains less defined. We previously reported that human telomerized bone marrow stromal cells support the generation of CD7+CD56- early T- as well as CD10+CD19+ early B-lymphoid precursors from human hematopoietic precursors. Here we examined whether and how early T lymphopoiesis is regulated by interaction with stromal cells. Low or no levels of LFA-1 were expressed on CD34+CD38-CD45RA- immature hematopoietic precursors. However, high levels of LFA-1 were detected on CD34+CD38-CD45RA+CD10+CD7+/-CD19- immature lymphoid precursors, while those of LFA-1 were diminished on CD34+CD38+CD45RA+CD10+CD19more mature pro B cells. On the other hand, ICAM-1 and ICAM-2 were expressed in a portion of the telomerized stromal cells. ICAM-3 was not detected. Various levels of ICAM-1, ICAM-2, or ICAM-3 were also expressed on hematopoietic and lymphoid precursors.

To examine the role of LFA-1-mediated adhesion to stromal cells or adjacent hematopoietic precccursors in early lymphoid differentiation, we examined the effect of anti-LFA-1 blocking antibody (Ab) on the differentiation of CD34+CD45RA-CD7-CD10-CD38lo/- hematopoietic precursors in the cultures on stromal cells or with conditioned medium (CM) obtained from cultures of stromal cells. In the cultures on stromal cells, anti-LFA-1 Ab strongly inhibited the generation of CD7+CD10-CD45RA+ and CD7-CD10+CD45RA+ lymphoid precursors from hematopoietic precursors after 21 days of culture. Significant number of CD14+monocytic cells was generated with or without anti-LFA-1 Ab. In the cultures with CM, anti-LFA-1 Ab showed marginable effect on lymphoid differentiation. To elucidate the effect of anti-LFA-1 Ab on more mature lymphoid precursors, CD7+CD10-CD45RA+ or CD7-CD10+CD45RA+ cells were isolated after culture of hematopoietic cells for 14 days and cultured on stromal cells in the presence or absence of anti-LFA-1 Ab. Anti-LFA-1 Ab remarkably inhibited the generation of CD7+ and CD10+CD19+ lymphoid cells from the CD7+CD10-CD45RA+ early T-lymphoid precursors. Notably, few or no CD45RA+CD14- lymphoid cells were detected. Anti-LFA-1 Ab did not affect B-lineage differentiation from CD10+CD19-CD45RA+ early B-lymphoid precursors to CD10+CD19+CD45RA+proB cells. We next examined which ICAM ligand is responsible for the observed effects by anti-LFA-1 Ab. Anti-ICAM-2 Ab inhibited the generation of CD7+CD45RA+ and CD10+CD45RA+ lymphoid precursors from CD34+CD45RA-CD7-CD10-CD38lo/- hematopoietic precursors on stromal cells, as observed with anti-LFA-1 Ab. No effect was observed with anti-ICAM-1 Ab. Anti-ICAM-2 Ab further suppressed the generation of CD7+ and CD10+ lymphoid cells from the cultured CD7+CD10-CD45RA+ early T-lymphoid precursors, but did not depress B-lymphoid differentiation from the cultured CD7-CD10+CD45RA+ early B-lymphoid precursors.

Taken together, these data indicate that LFA-1-mediated adhesion to ICAM-2 is essential for stromal cell-dependent early lymphoid differentiation of hematopoietic and CD7+ early T-lymphoid precursors.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH