Using lymph node transplantation as an approach to image cellular interactions between the skin and draining lymph nodes during parasitic infections

Abstract

The growing use of protozoan parasites expressing fluorescent reporter genes, together with advances in microscopy, is enabling visualisation of their behaviour and functions within the host from the very earliest stages of infection with previously unparalleled spatiotemporal resolution. These developments have begun to provide novel insights, which are informing our understanding of where host immune responses may be initiated, which cells are involved and the types of response that are elicited. Here we will review some of these recent observations that highlight the importance of cellular communication between the site of infection and the draining lymph node (dLN) in establishing infection and immunity. We also highlight a number of remaining challenges and unknowns that arise through our inability to follow and fate map the journey of a single cell between spatially separated tissue sites. In response to these challenges, we review a recently described experimental strategy that extends the spatial and temporal limits of previous imaging approaches, most significantly allowing longitudinal analysis of cellular migration between the skin and draining lymph nodes in vivo, without the requirement for invasive surgery.

Keywords: Immunology; In vivo imaging; Infection; Microscopy.

Graphical abstract

Fig. 1

Outstanding questions during the initial stages of protozoan infection. Following inoculation into the skin after arthropod bite, gaps remain in our understanding of the interactions between parasites (red) and parasite antigen with host cells (green), such as DCs. In particular, it has been difficult to investigate parasite location and trafficking to the LN, via lymphatic and/or blood vessels, A). Major questions remaining about parasite (red) and host (green) behaviour are listed, B); depicted in A). In order to address these questions, several obstacles will need to be overcome, C); some possible solutions to these are listed, D).

Fig. 2

Implantation of a lymph node into the ear pinna. The process of LN implantation into the mouse ear pinna. The ear is secured and a pouch is formed, A); the LN is inserted into the pouch, B); and veterinary adhesive used to seal the opening, C). Implanted tissue may be vizualised by X-ray, D). An example section of an implanted LN, stained using DAPI, and antibodies recognizing B220 and CD4, E).