Indeed, VEGFR TKIs have been associated with reversal of immune suppression in

In the current study we aimed to investigate the kinetics and location of the immune complexes in more detail and to test the hypothesis that the perivas cular drainage of solutes is affected under these condi tions. To analyze immune complex formation following intracerebral OVA injection at different time points, we first stained [You must be registered and logged in to see this link.] tissue from non immunized and OVA im munized mice for OVA, IgG, and C3. Laminin was used to identify the location of the immune complex within the blood vessel wall . Five minutes and three hours after its injection in immunized mice, OVA was diffusely spread in the ipsilateral striatum, corpus callosum and cortex as described previously . Around the injection site for OVA, Complement C3 and IgG were present on both sides of the laminin of capillaries of OVA immunized mice .

IgG was seen within the lumen of blood vessels, with little extravasa tion in the perivascular space. The staining for C3 was diffuse and limited only to the injection site, without any C3 observed in [You must be registered and logged in to see this link.] basement membranes. Non immunized control mice showed minimal levels of IgG and C3 . At twenty four hours, IgG, C3 and OVA were identi fied in the brain in close proximity to the cerebral vascu lature and double staining for IgG and laminin revealed that IgG and complement C3 were present in the paren chyma and also co localized with laminin present in the walls of blood vessels . Staining for IgG, OVA, C3 and C1q confirmed the presence of immune complexes in the parenchyma and their association with blood vessels . OVA was no longer detectable in association with the cerebrovascular basement mem branes at 7 days .

Reduced perivascular drainage [You must be registered and logged in to see this link.] of dextran tracer in the presence of immune complexes Having demonstrated that immune complexes are formed in the basement membrane, 24 h, but not yet at 5 minutes, after intracerebral injection of OVA, we next investigated perivascular drainage in the presence of immune complexes by co injecting a fluorescent tracer at 5 minutes, 24 h and 7 days following the intracerebral injection of OVA. We previously showed that within five minutes of its injection, fluorescent dextran spreads diffusely and is found at the basement membranes of cerebral capillaries of the grey matter . Therefore we used this time point to test if drainage of dextran is impeded following im mune complex formation in the basement membranes of cerebral blood vessels.

In a separate group of mice, we allowed dextran to drain for 24 h. Five minutes after OVA injection, we observed a dif fuse distribution of the fluorescent tracer dextran in the extracellular space and within the walls of capillaries and arteries of OVA immunized mice . This pat tern was similar to non immunized, control animals . Quantification of the type of vessels that contained dextran associated with their walls re vealed that at 5 minutes after injection of OVA, there was no difference in the number of dextran positive ar teries or capillaries, compared to non immunized con trols . Furthermore, there were no differences in the number of veins labeled with dextran between this group and control animals . At 24 h after OVA injection, dextran had a reticular cuff appearance around laminin in the walls of capillaries and arteries .