Figure 2. Virally infected astrocytes display a different phenotype when contacted by T cells.

Astrocytes contacted by infiltrating T cells display various alterations in morphology in comparison with cells not contacted. According to the degree of morphological alteration, the morphologies of contacted cells were further classified into the four categories illustrated in (A). In (A) target astrocytes are represented as blue stellate shapes, while contacting T cells are represented as round yellow shapes. The confocal micrographs illustrate Category 1–4 infected target cells immunolabeled for TK (white) and T cells immunolabeled for TCR (red). Category 1 includes virally infected cells (i.e., expressing TK) with T cells contacting regular processes (<2 μm in diameter); Category 2 includes virally infected cells with T cells contacting a protrusion (a cell process >2.5 μm in diameter); Category 3 includes virally infected cells with T cells in contact with the cell body with obvious cytoplasm between the cells; and Category 4 includes virally infected cells with T cells in contact with the cell body without obvious cytoplasm between the two cells. (B) shows confocal images of virally infected cells (TK, white) either contacted by T cells (right panel, TCR, red), or non-contacted (left panel). A significantly higher proportion of virally infected, contacted cells displayed protrusions (93%) when compared to virally infected but non-contacted cells (45%) (p<0.05, Chi square test); white arrows indicate a branching protrusion in a non-contacted astrocyte in the left panel, and an astrocyte protrusion contacting a T cells in the right panel. (C) shows the number of processes, (D) the diameter of the processes, and (E) the diameters of protrusions in virally infected cells, either contacted by T cells or non-contacted. The left histograms in (C) through (E) compare contacted versus non-contacted cells; 1–4 are categories as described in (A). Numbers and percentages of cells in each category are indicated inside each bar. Note that the number of processes and their diameters are significantly reduced in contacted cells (* p<0.05; Student's t test). The reduction in process number is evident in categories 2 and higher (C, * p<0.05 v. Category 1; one way ANOVA), while the reduction in process diameter is seen in all categories of contacted cell.