Effector CD4⁺ T cells are well-recognised for their capacity to respond to antigen and induce antigen-specific inflammation after they exit the vasculature. However in some diseases, such as T cell-mediated glomerulonephritis, the disease-initiating antigen is often located within the vasculature. The mechanisms of CD4⁺ T cell antigen recognition under these circumstances are not well understood. Here we examined this issue using intravital multiphoton microscopy of mouse kidneys. Direct visualisation of glomeruli revealed that effector CD4⁺ T cells undergo spontaneous intravascular retention and migration in uninflamed glomeruli. While MHCII was not expressed by intrinsic glomerular cells, intravascular MHCII-expressing immune cells extensively patrolled glomerular capillaries, regularly interacting with intraglomerular CD4⁺ T cells. Following targeted deposition of cognate antigen in glomeruli, CD4⁺ T cells trafficking through glomeruli displayed responses consistent with antigen recognition, including increased recruitment, decreased migration and elevated expression of CD69 and IFNγ. Of the MHCII⁺ leukocytes present in the circulation, both B cells and monocytes underwent retention in glomerular capillaries, although MHCII⁺ monocytes were typically retained in the glomerulus over much longer durations, providing them greater opportunity to encounter intraglomerular CD4⁺ T cells. Furthermore, while the absence of B cells did not affect CD4⁺ T cell-dependent glomerular inflammation, monocyte depletion attenuated this response. These studies provide evidence that antigen within the glomerular microvasculature is presented to intravascular effector CD4⁺ T cells by MHCII-expressing monocytes patrolling glomerular capillaries, leading to initiation of antigen-dependent glomerular inflammation.