Provided herein are D domain containing polypeptides that specifically bind targets of interest, as are nucleic acids encoding the D domain containing polypeptides, vectors containing the nucleic acids and host cells containing the nucleic acids and vectors. Also provided herein are methods of making and using the D domain containing polypeptides, nucleic acids, vectors and host cells, for example, but not limited to, in diagnostic and therapeutic applications. Also provided herein are multi-functional chimeric antigen receptor (CAR)-based compositions and Adapters and their use in methods of directing immune responses to target cells. In some embodiments, the methods include the use of a CAR expressing cell in combination with an Adapter. The Adapter confers the ability to modulate, alter, and/or direct CAR expressing cell-mediated immune response in vitro and in vivo.

The use of Fc-tagged Pregnancy-specific glycoprotein 1 (PSG1-Fc) in a method of treatment of a tendon injury in a human, in which the PSG1 is administered by intra-tendon or peri-tendon injection, is described. Also described is the use of CC49 in a method of treatment of tendonitis, tendinosis, tendinopathy, or tendon damage in an equine mammal, in which the CC49 is administered by intra-tendon or peri-tendon injection.