Status of platelet-lymphocyte aggregation in circulating blood of patients with type 1 diabetes with and without diabetic nephropathy.

BACKGROUND: Platelets can modulate the role of lymphocytes in the development of micro- and macrovascular complications in type 1 diabetes mellitus. OBJECTIVES: To clarify the status of platelet-lymphocyte aggregation in circulating blood in patients with T1DM, as well as the differences in the platelet-lymphocyte aggregation in T1DM patients with and without diabetic nephropathy. METHODS: We recruited 115 T1DM patients (47 men and 68 women) aged 15-52 years. The subjects with mean albumin excretion > or = 5 microg/mg creatinine comprised group 1, and those with < 5 microg/mg creatinine comprised group 2. The matched healthy participants (n=50) served as the control group. Detection of LPA was achieved using a light microscope after Ficoll-gradient centrifugation. Immunophenotyping of lymphocytes was performed by flow cytometry. RESULTS: Significantly more LPA (430.4 +/- 20.6/microl) were observed in group 2 compared with group 1 (223.9 +/- 12.8/microl, P< 0.001) and the control group (296.1 +/- 22.6/microl, P=0.027). In group 1 significantly more LPA/CD4 (21.1 +/- 1.6%) and LPA/(CD4 + NK) (17.8 +/- 1.7%) were found than in group 2 and the control group. CONCLUSION: T1DM with diabetic nephropathy is associated with higher levels of LPA than T1MD without diabetic nephropathy. The role of LPA in microvascular complications in diabetes should be elucidated in further studies.

Platelets enhance CD4+ lymphocyte adhesion to extracellular matrix under flow conditions: role of platelet aggregation, integrins, and non-integrin receptors.

The purpose of this study was to examine the role of platelets in CD4+ T lymphocyte adhesion to subendothelial extracellular matrix (ECM). Herpesvirus saimiri (HVS)-infected CD4+ T cells were incubated on ECM. An image analysis was used to evaluate T cell adhesion. Under static condition, T cell activation with 4-alpha-Phorbol 12-myristate 13-acetate (PMA) resulted in a 2.6-fold increase in cell adhesion. However, adhesion was not affected by platelets. In contrast, under flow (200s(-1)), platelets markedly enhanced both resting and PMA-activated T cell adhesion (33- and 48-fold), forming lymphocyte-platelet co-aggregates that contain approximately 90% of the adherent T cells. Abrogation of platelet aggregation with tirofiban inhibited formation of platelet-T cell co-aggregates under flow and reduced T cell adhesion by 74%. Separate and combined blockade of CD40L and P-selectin glycoprotein-1 (PSGL-1) on PMA-activated lymphocytes reduced adhesion under flow in the presence of platelets by 28%, 33%, and 55%, respectively. Blockade of beta1-integrins decreased adhesion under both static and flow conditions (by 35% and 44%, respectively), while blockade of beta2-integrin reduced adhesion only under static condition (by 23%). A similar adhesion pattern was observed using CD4+ T cells isolated from normal donor peripheral blood. In conclusion, platelets support CD4+ lymphocyte adhesion to ECM under flow by formation of heterotypic platelet-lymphocyte coaggregates involving alphaIIbbeta3 integrin and beta1-related integrins, as well as CD40L and PSGL-1.

Lymphocyte-platelet crosstalk in Graves' disease.

OBJECTIVE: Platelets can modulate lymphocytes' role in the pathophysiology of thyroid autoimmune diseases. The present study was performed to clarify the status of platelet-lymphocyte subpopulations aggregation in circulating blood in patients with Graves' disease (GD). METHODS: One hundred and fifty patients with GD (GD group) and 45 hyperthyroid patients with toxic multinodular goiter (TMG group) were recruited in the study. Control group consisted 150 healthy subjects. Immunophenotyping of lymphocytes was performed by flow cytometry. Detection of lymphocyte-platelet aggregates (LPAs) was done using light microscope after Ficoll-gradient centrifugation. RESULTS: The group of GD patients exhibited reduced CD8 lymphocyte and higher CD19 cell counts compared with TMG group and healthy controls. A greater number of activated CD3, HLA-DR+ lymphocytes were observed in GD than in TMG group and control group. GD group was characterized by lower blood platelet count (232 ± 89 × 10 cells/µL) than TMG group (251 ± 97 × 10 cells/µL; P < 0.05) and control group (262 ± 95 × 10 cells/µL; P < 0.05). In GD group, more platelet-bound lymphocytes (332 ± 91 /µL) were found than that in TMG group (116 ± 67/µL, P < 0.005) and control group (104 ± 58 /µL; P < 0.001). CONCLUSIONS: GD is associated with higher levels of activated lymphocytes and lymphocyte-platelet aggregates.

CD4+ lymphocytes require platelets for adhesion to immobilized fibronectin in flow: role of beta(1) (CD29)-, beta(2) (CD18)-related integrins and non-integrin receptors.

The role of platelets in T-lymphocytes adhesion is not clear yet. Herpesvirus saimiri (HVS)-infected CD4(+) T-lymphocytes were placed into polystyrene plates pre-coated with fibronectin. The adherent T-cells were enumerated by image analysis. Under static condition, 38+/-10cells/mm(2) adhered and addition of gel-filtered platelets (GFP) and PMA enhanced cell adhesion 4.3- and 4.1-fold. Using PMA plus GFP 11.9-fold enhancement in cell adhesion was achieved. In contrast, under flow (200s(-1)), neither basal adhesion nor following separate addition of PMA or GFP was observed, whereas combined addition of PMA and GFP induced noticeable adhesion (34cells/mm(2)). The adhesion was inhibited by blockade of alpha(5)-integrin (CD49e, 87%), beta(2)-integrin (CD18, 78%), CD40L (60%), PSGL-1 (CD162, 60%), and CD40L plus PSGL-1 (83%). Thus, activated platelets promote activated T-cell adhesion to fibronectin under flow via integrins (alpha(5)beta(1), and alpha(L)beta(2)), CD40-CD40L and P-selectin-PSGL-1 mediated interactions.