Sculptra acts as a biostimulant that creates collagen in the lower dermis, and the beneficial effects last 1-2 years. If injected in blobs or clumps (it is a viscous product that has some technique-related issues) nodules can result, but this is not an "auto-immune" response; this is what is intended with Sculptra use. Collagen formation is what provides the volume restoration intended with Sculptra use.
The same thing happens with Vicryl sutures, which are made of the same material as Sculptra (poly-L-lactic acid)--collagen replaces the suture as it dissolves, leaving the wound or incision line securely connected by new collagen formation that provides strength and cohesion to the scar.
If people didn't have a collagen response to Sculptra, it wouldn't "work," and if it didn't last long-term then it wouldn't be a satisfactory product to use for that indication. Shorter-term needs for filler are commonly achieved with HA (hyaluronic acid) filler such as Juvederm or Restylane.
Best wishes! Dr. Tholen