The movement of a leukocyte within or between different tissues and organs of the body as part of an immune response. [ http://www.ncbi.nlm.nih.gov/pubmed/14680625 http://www.ncbi.nlm.nih.gov/pubmed/7507411 http://www.ncbi.nlm.nih.gov/pubmed/8600538 https://www.worldcat.org/search?q=bn%3A0781735149 http://www.ncbi.nlm.nih.gov/pubmed/14708592 ]