Functional T-cell responses are initiated by physical interactions between T-cells and antigen-presenting cells (APCs), including dendritic cells (DCs) and B-cells. T-cells are activated more effectively by DCs than by B-cells, but little is known about the key molecular mechanisms that underpin the particular potency of DC in triggering T-cell responses. To better understand the influence of physical intercellular interactions on APC efficacy in activating T-cells, we used single cell force spectroscopy to characterize and compare the mechanical forces of interactions between DC:T-cells and B:T-cells. Following antigen stimulation, intercellular interactions of DC:T-cell conjugates were stronger than B:T-cell interactions. DCs induced higher levels of T-cell calcium mobilization and production of IL-2 and IFNγ than were elicited by B-cells, thus suggesting that tight intercellular contacts are important in providing mechanically stable environment to initiate T-cell activation. Blocking antibodies targeting surface co-stimulatory molecules CD80 or CD86 weakened intercellular interactions and dampen T-cell activation, highlighting the amplificatory roles of CD80/86 in regulating APC:T-cell interactions and T-cell functional activation. The variable strength of mechanical forces between DC:T-cells and B:T-cell interactions were not solely dependent on differential APC expression of CD80/86, since DCs were superior to B-cells in promoting strong interactions with T-cells even when CD80 and CD86 were inhibited. These data provide mechanical insights into the effects of co-stimulatory molecules in regulating APC:T-cell interactions.

The prevalence of diabetes mellitus (DM) is projected to approach 600 million people worldwide by 2035 and there are concerns about a potential diabetes epidemic in Asia. 1 Diabetic retinopathy (DR), a complication of DM, afflicts a third of diabetics and is the principal cause of vision loss among the working age group in developed countries 2 and remains a leading cause of preventable blindness. 3 The proportion of visual impairment worldwide caused by DR has increased. 4 Diabetic macular edema (DME), characterized by increased vascular permeability and the deposition of hard exudates at the central retina, can develop at any stages of DR and afflicts 21 million people globally. 5Through regular eye examinations and adequate DM management, the diabetes-related vision loss can be prevented in 98% of cases. 6,7 Primary interventions, such as intensive glycemic and blood pressure control, can reduce the incidence and progression of DR and DME, while secondary interventions, such as laser photocoagulation and injections of anti-vascular endothelial growth factor drugs, may prevent development and progression of vision loss. [8][9][10][11][12][13] Therefore, early detection of DR and DME through screening programs and appropriate referral for therapy are essential to preserving vision in individuals with diabetes. DR screening has been shown to be a cost-effective method of preventing diabetes-related vision loss.14,15 Since blindness from DR and DME is preventable from both public health screening and clinical management perspectives, it is important to precisely identify persons who have DR/DME for early intervention before they progress to severe visionthreatening stages. 16Current DR screening programs typically employ retinal fundus photography and manual assessment of DR, 17 but this approach requires highly skilled readers which is labor-intensive and costly. Moreover, fundus photography as a technique Abstract Due to the increasing prevalence of diabetes mellitus, demand for diabetic retinopathy (DR) screening platforms is steeply increasing. Early detection and treatment of DR are key public health interventions that can greatly reduce the likelihood of vision loss. Current DR screening programs typically employ retinal fundus photography, which relies on skilled readers for manual DR assessment. However, this is labor-intensive and suffers from inconsistency across sites. Hence, there has been a recent proliferation of automated retinal image analysis software that may potentially alleviate this burden cost-effectively. Furthermore, current screening programs based on 2-dimensional fundus photography do not effectively screen for diabetic macular edema (DME). Optical coherence tomography is becoming increasingly recognized as the reference standard for DME assessment and can potentially provide a cost-effective solution for improving DME detection in large-scale DR screening programs. Current screening techniques are also unable to image the peripheral retina and require pharmacological pupil dilation; ul...