Here is the original slide:
I am thinking about the "cord factor" sentence in a more general case.
Assume you inhibit Leucocytes migration. How does this lead to accumulation of macrophages in the site of infection?
The mechanism is likely very straightforward. Activated macrophages already in the area are releasing pro-inflammatory cytokines like TNFα, IL-1β, IL-6, IL-12, MIP-2, etc. These are not only important for granuloma formation, but they also recruit other immune cells to the area. However, since cord factor has this anti-migratory effect, once the cells get there they can't leave. This is important because activated macrophages are key antigen-presenting cells (once they kill and break down the antigen, in this case Mycobacteria), and they need to move to the spleen to assist in the upregulation of the adaptive immune response. By preventing this, mycobacteria can evade part of the immune system - part of the reason why TB is so hard to clear once acquired.