We can see the long range content of these jets when they are pointed directly at us as "blazars" which do produce positrons. "Gas, dust and the occasional sta

We can see the long range content of these jets when they are pointed directly at us as "blazars" which do produce positrons. "Gas, dust and the occasional star are captured and spiral into this central black hole, creating a hot accretion disk which generates enormous amounts of energy in the form of photons, electrons, positrons and other elementary particles." https://en.m.wikipedia.org/wiki/Blazar https://en.m.wikipedia.org/wiki/Blazar The general discussion of astrophysical jets describe them as formed from regular matter. There would be some quantity of antimatter initially, but it would quickly be consumed and converted to gamma rays. https://en.m.wikipedia.org/wiki/Astrophysical_jet https://en.m.wikipedia.org/wiki/Astrophysical_jet