The MSMQ-MQSeries Bridge, which ships with Host Integration Server 2006 (HIS 2006) and earlier, is a well-established way to integrate the messaging worlds of Microsoft and IBM.
The Bridge is essentially a Windows application written to use the MQSeries (or more accurately WebSphere MQ) APIs to manage message flow to and from IBM hosts (that is, mainframes or servers running Windows, Solaris, Linux, etc.). Messages can be pulled from local MSMQ queues and sent through the MQSeries client to remote MQSeries queues, or pulled from those same remote MQSeries queues and placed in the local MSMQ queues.
Being dependent on the WebSphere MQ client, the Bridge can only be installed on operating systems where there could be a Windows client to work with. For example, IBM does not currently supply a true 64-bit client for Windows so HIS 2006 will not provide the option to select the Bridge when setup is run on 64-bit operating systems. (Note: setup detects the operating system and not the presence of the WebSphere MQ client so the introduction of a true 64-bit client will not cause setup to do anything different).