I am working with Jurkat cells to see the binding of the anti-CD3 single chain to the Jurkat cells. When I am binding my fusion antiPSMA X anti CD3 to the Jurkat cells, I see but a very small percentage of the cells binding but when I am using only anti-CD3 single chain for the jurkat binding I see that there is no binding. Jurkat seems to form clusters under the microscope, can that be a reason that only part of the population binds and the part remains inaccessible to the fusion or the single chain?

Any answers will be very helpful and greatly appreciated.