some chapters also have strong ties to the various inquisitorial ordos; for example the ultramarines, emperor's scythes and lamenters collectively have very strong ties to the ordo hereticus and battle-brothers from these three chapters form a large number of specialised kill-teams trained to fight tyranids!
the ultramarines especially owe their very exisitance to the now renegade lord inquisitor kryptman and thus are honour-bound to answer his calls for aid when nearby worlds come under threat from the great devourer
other chapters such as the iron hands who are very puritanical by nature wouldn't ask twice if an inquisitor requested their aid in purging any heretical cults! (indeed, they are famed for their brutal and blind supression of any populations that are found to be disloyal to the Emperor!)
cheers!