Binding Of Peripheral Blood Lymphocytes Research Articles

Interaction of acute lymphopblastic leukemia cells with C-type lectins DC-SIGN and L-SIGN

The C-type lectins DC-SIGN (CD209) and L-SIGN (CD299) recognize defined carbohydrates expressed on pathogens and cells. Those lectins are expressed on dendritic cells (DC) and/or on liver-sinusoidal endothelial cells. Both cell types modulate immune responses. In acute lymphoblastic leukemia (ALL), aberrant glycosylation of blast cells can alter their interaction with the C-type lectins DC-SIGN and L-SIGN, thereby affecting their immunological elimination. We investigated whether recombinant DC-SIGN and L-SIGN bind to blood or bone marrow cells from B- and T-ALL patients and compared that with binding of peripheral blood lymphocytes from healthy donors. It was found that increased binding of ALL cells to DC-SIGN and L-SIGN was observed compared to cells from healthy donors. Furthermore, L-SIGN bound a higher percentage of leukemic and normal cells than DC-SIGN. B-ALL bone marrow cells showed the highest binding to L-SIGN. DC-SIGN bound equally well to B-ALL and T-ALL cells. Within ALL subtypes, DC-SIGN binding was higher with mature T-ALL. Interestingly, our data demonstrate that increased binding of DC-SIGN and L-SIGN to peripheral leukemic cells from B-ALL patients is associated with poor survival. These data demonstrate that high binding of B-ALL peripheral blood cells to DC-SIGN and L-SIGN correlates with poor prognosis. Apparently, when B-ALL cells enter the blood circulation and are able to interact with DC-SIGN and L-SIGN the immune response is shifted toward tolerance. Additional studies are necessary to ascertain the possible role of these results in terms of disease pathogenesis and their potential as target to eradicate leukemic cells.

Selective binding of peripheral blood lymphocytes to the walls of cerebral vessels in frozen sections of human brain

In order to identify the factor that control the binding of blood leucocytes to cerebral blood vessels we have modified and applied the frozen section assay of Stamper and Woodruff to the study of human brain. Cryostat sections of brain tissue obtained at post mortem were overlaid with blood lymphocytes and experimental conditions were defined which permitted optimum binding of the cells to transected blood vessel walls. The maximal binding of lymphocytes to cerebral vessels occurred when 6 × 10 6 lymphocytes were overlaid onto brain sections for 30 min at 7°C with gentle agitation. Only a small proportion (0.01%) of the added lymphocytes bound to exposed cerebral vessels. However, lymphocytes were far more adherent than monocytes and polymorphonuclear cells (7-fold and 11-fold respectively: p < 0.001) and activation of lymphocytes with IL-2 enhanced their binding to blood vessel walls (mean 130% increase; p < 0.03). Further analysis revealed that CD4-positive T lymphocytes were the predominant cell population binding to the blood vessels. Antibody blocking studies showed that lymphocyte binding to cerebral blood vessels was inhibited by pretreating the lymphocytes with anti-CD11a, anti-CD18 or anti-CD49d ( p ≤ 0.02) and immunohistochemical studies revealed the presence of the counter-receptors ICAM-1 (CD54) and VCAM-1 (CD106) for these adhesion molecules in addition to the presence of E-selectin (CD62E) and P-selectin (CD62P) on the cerebral blood vessels. The establishment of a technique in situ which measures selective binding of CD4-positive peripheral lymphocytes to sections of cerebral blood vessels will assist in the molecular characterization of factors that control the interaction of leucocytes with the blood-brain barrier in health and disease.

Bromelain protease F9 reduces the CD44 mediated adhesion of human peripheral blood lymphocytes to human umbilical vein endothelial cells

The thiol protease bromelain has been shown to remove T-cell CD44 molecules from lymphocytes and to affect T-cell activation. We investigated the effect of a highly purified bromelain protease F9 (F9) on the adhesion of peripheral blood lymphocytes (PBL) to human umbilical vein endothelial cells (HUVEC). Preincubation of the lymphocytes with F9 reduced the adherence to about 20% of unstimulated and to about 30% of phorboldibutyrate (P(Bu) 2) stimulated lymphocytes. Using flow cytometry, both crude bromelain and protease F9 reduced the expression of CD44, but not of LFA-1, on PBL. F9 was about 10 times more active than crude bromelain; at 2.5 μg/ml of F9 about 97% inhibition of CD44 expression was found. A mAb against CD44 was tested and found to block the F9-induced decrease in PBL-binding to HUVEC. The results indicate that F9 selectively decreases the CD44 mediated binding of PBL to HUVEC.

Regulation of natural killer cell activity by transforming growth factor-beta and prostaglandin E2.

The separate and combined effects of transforming growth factor-beta 1 (TGF-beta 1) and prostaglandin E2 on human natural killer (NK) activity were studied. Peripheral blood lymphocytes (PBL) and large granular lymphocytes (LGL, 70-90% purity) were used as effector cells and K562 as targets. Overnight incubation of the effector cells with TGF-beta 1 resulted in a significant inhibition of NK activity. TGF-beta 1 did not influence the expression of CD3, CD16, CD18 or CD56 antigens on PBL. Combination of TGF-beta 1 with indomethacin gave the same NK-suppressive effect as TGF-beta 1 alone, showing that the inhibition of NK activity by TGF-beta 1 is not due to an increase in PGE2 levels. TGF-beta did not influence cAMP level in PBL whereas PGE2 significantly increased it. On the other hand, TGF-beta 1 and PGE2 showed an additive inhibitory effect on NK activity. TGF-beta 1 did not reduce the binding of PBL and LGL to K562. PGE2 suppressed the binding and TGF-beta 1 did not influence this suppression. TGF-beta 1 also suppressed IL-2-induced activation of NK activity and increase of expression of the granule proteins granzyme A and perforin. PGE2 did not appear to affect granzyme A and perforin contents. The results indicate that TGF-beta 1 and PGE2 suppress NK activity by different mechanisms.

Interleukin 4 and tumour necrosis factor alpha induce different adhesion pathways in endothelial cells for the binding of peripheral blood lymphocytes.

We demonstrated that tumour necrosis factor alpha (TNF-alpha) and interleukin 4 (IL-4) increased endothelial cell (EC) adhesiveness for peripheral blood lymphocytes (PBL) by promoting transcription and protein synthesis. The different kinetics observed with TNF-alpha and IL-4 suggest the involvement of different adhesion molecules. Blocking adhesion assays and immunofluorescence analysis showed that PBL adhesion to endothelial cells involves different pair adhesion molecules. Whereas IL-4 promoted an LFA-1-dependent/ICAM-1-independent adhesion pathway on EC, TNF-alpha stimulated an LFA-1-dependent/ICAM-1-dependent adhesion pathway on EC. In contrast, VLA-4/VCAM-1 molecules were involved in PBL adhesion both to IL-4 and to TNF-alpha-stimulated EC. Finally, we found that a CD2-dependent/LFA-3-independent adhesion pathway was mainly involved in IL-4-stimulated EC.

The streptococcal preparation OK-432 specifically augments the susceptibility of human urinary bladder tumor cells to autologous peripheral blood lymphocytes.

The streptococcal preparation OK-432 was tested for its ability to enhance the susceptibility of fresh urinary bladder tumor (UBT) cells to autologous peripheral blood lymphocytes (PBL) in patients with UBT. PBL treated with OK-432 at 0.1 Klinishe Einheit (KE)/ml for 18 hours killed the human T24-lined UBT cells and freshly separated autologous UBT cells more efficiently than untreated PBL. Treatment of K562 erythroleukemia cells with OK-432 at 0.1 KE/ml for 18 hours had no effect on their susceptibility to lysis by fresh PBL. In contrast, treatment of T24 and fresh autologous UBT cells with OK-432 resulted in an enhancement of their susceptibility to PBL. The susceptibility of autologous UBT cells to both large granular lymphocytes (LGL) and T-lymphocytes was also enhanced by treatment of tumor cells with OK-432. Binding of PBL to T24 and fresh autologous UBT cells was also augmented by treatment of the tumor cells with OK-432. The frequency of binding of OK-432 to fresh UBT cells was positively correlated with the increased target sensitivity to autologous PBL. The inhibition of RNA synthesis in fresh UBT cells by OK-432 was also associated with the elevated susceptibility to autologous PBL. These results indicate that OK-432 activates the autologous tumor killing system through stimulation of effector cells and elevation of target susceptibility to effector cells in patients with UBT, and suggest that the OK-432-augmented target sensitivity to PBL may be oriented specifically to UBT cells and local immunotherapy with OK-432 may be remarkably beneficial in the treatment of UBT.

A monoclonal antibody to beta 1 integrin (CD29) stimulates VLA-dependent adherence of leukocytes to human umbilical vein endothelial cells and matrix components.

The leukocyte beta 1 integrin receptor very late activation antigen-4 (VLA-4) (alpha 4 beta 1, CD49d/CD29) binds to vascular cell adhesion molecule-1 (VCAM-1) expressed on cytokine-activated endothelium. A mAb designated 8A2 was identified that stimulated the binding of U937 cells to CHO cells transfected with VCAM-1 cDNA but not endothelial-leukocyte adhesion molecule or CD4 cDNA. mAb 8A2 also rapidly stimulated the adherence of peripheral blood lymphocytes (PBLs) to VCAM-1-transfected CHO cells or recombinant human tumor necrosis factor-treated human umbilical vein endothelial cells. mAb 8A2-stimulated binding of PBL was inhibited by mAbs to VLA-4 or VCAM-1. Surface expression of VLA-4 was not altered by mAb 8A2 treatment and monovalent Fab fragments of mAb 8A2 were active. Immunoprecipitation studies reveal that mAb 8A2 recognizes beta 1-subunit (CD29) of integrin receptors. In contrast to mAbs directed to VLA-4 alpha-subunit (alpha 4, CD49d), mAb 8A2 did not induce homotypic aggregation of PBL. Additionally, mAb 8A2 stimulated adherence of PBL and hematopoietic cell lines to purified matrix components laminin and fibronectin. This binding was blocked by mAbs to the VLA alpha-subunits alpha 6 (CD49f), or alpha 5 (CD49e) and alpha 4 (CD49d), respectively. We conclude that mAb 8A2 modulates the affinity of VLA-4 and other leukocyte beta 1 integrins, and should prove useful in studying the regulation of beta 1 integrin function.

A monoclonal antibody that blocks class II histocompatibility-related immune interactions

Previous studies using conventional hetero- or isoantisera have indicated the involvement of class II (Ia) molecules in presentation of soluble by monocytes to inducer T lymphocytes, stimulation of inducer T cells in MLR, and recognition of Ia-bearing targets cells by cytotoxic T lymphocytes (CTL). The experience in using monoclonal anti-Ia reagents capable of blocking these phenomena in the human system is limited. Recently, however, we have characterized a lytic IgG2a monoclonal antibody, 9–49, that binds to functionally significant class II molecules. This antibody blocks (in the absence of complement): (1) specific binding of peripheral blood lymphocytes (PBL) to antigen-pulsed monocyte monolayers, (2) proliferation of PBL in response to soluble antigen (tetanus toxoid or mumps) or cell surface class II antigen stimulation in allogeneic or autologus MLR, (3) proliferation of cloned T4+ (inducer) lymphocyte cell lines to class II antigens, (4) generation of cytotoxic lymphocytes during allogenic MLR, and (5) recognition (and killing) of class II-bearing target cells by T4+ CTL clones. Proliferation and CTL activity of a T8+ clone is unaffected by the 9–49 antibody. These results indicate the usefulness of this monoclonal reagent in studies evaluating the functional role of Ia molecules in immune recognition phenomena.