You will need to discuss with your immunologist to see if they think there is a specific reason you are getting urinary infections but in general the immune system does not play a role in protecting the lower urinary tract as this is really dependent on good bladder hygiene (voiding often and not holding urine) and normal anatomy.  Low IgA and low MBL are both very common in the healthy population and would not usually be considered a cause for urine infections.