The Council of Science Editors recently organized the participation of 232 journals worldwide in its 2007 Global Theme Issue on Poverty and Human Development. In this issue, Nature Immunology is pleased to contribute two commentaries by Farrar (p 1277) and Gotch and Gilmour (p 1273) discussing this topic. Articles contributed by Nature Publishing Group are freely accessible at http://www.nature.com/povhumdev/index.html. Artwork by Lewis Long.

Many initial encounters between host and pathogenfor example, the stinging bite of a malaria-infected mosquito (shown here)cause no disease, but when infection does take hold, a complex chain of interactions between host and pathogen occurs that defines the outcome. In a series of specially commissioned articles and additional online material, host-pathogen interactions are explored (http://www.nature.com/ni/focus/pathogenesis/). Artwork by Lewis Long.

50 years ago saw the publication of the clonal selection theory by Frank Macfarlane Burnet, pictured here. This month we celebrate this landmark in immunology with a special commentary by Hodgkin, Heath and Baxter, accompanied by the republication of Burnet's clonal selection theory. Original photograph courtesy of the Walter and Eliza Hall Institute. Artwork by Lewis Long.

Whether CD8+ T cells, like CD4+ T cells, provide 'help' to other T cells is not clear. Amigorena and colleagues demonstrate that antigen-specific CD8+ T cells 'help' naive CD8+ T cells by promoting the interaction of naive CD8+ T cells with antigen-bearing dendritic cells. The original time-lapse video image shows antigen-specific CD8+ T cells (red) interacting with antigen-bearing dendritic cells (gray). Naive CD8+ T cells are shown in green. Artwork by Lewis Long.

Pei and colleagues report that β-arrestin 1 promotes expression of the prosurvival molecule Bcl-2 in autoreactive CD4+ T cells (p 817, see also News and Views by Frederick and Miller, p 791). The original image (bottom; by Jingwu Z. Zang) shows the spinal cord of a mouse with experimental autoimmune encephalomyelitis with infiltrating CD3+ cells (green) near leptomeningeal vessels stained for vWF (red), an endothelial cell marker. Nuclei are counterstained with DAPI (blue). Artwork by Lewis Long.

Lymph nodes bar entry to previously activated cytotoxic T cells. Inflammatory signals, however, activate lymph nodes to transiently express CXCL9 on high endothelial venules. Sallusto and colleagues report that 'killer' T cells, responding to the CXCL9 cue, can re-enter inflamed lymph nodes to eliminate antigen-presenting dendritic cells. The original image (by Miroslav Hons and Federica Sallusto) shows CXCL9 (red) on lymph node high endothelial venules surrounded by fibers of the fibroblastic reticular cell network (green). Artwork by Lewis Long.

Reis e Sousa and colleagues report that stimulation of dectin-1 on dendritic cells by candida elicits CARD9-dependent signaling that leads to the development of TH-17 cells (p 630; see also News and Views by Palm and Medzhitov, p 549). The original image (bottom; by Alexander D. Edwards and Caetano Reis e Sousa) shows bone marrow-derived dendritic cells stained with phalloidin to demonstrate polymerized actin filaments. Artwork by Lewis Long.

As a nudge produces a cascade of toppling dominos, a transcription factor initiates a series of cellular processes that subsequently direct lymphocyte lineage differentiation. The resulting lineage identity is malleable, however, sometimes 'bending' with changes in the lineage specification factors present. In a series of specially commissioned articles this month, we focus on transcription factors that influence lymphocyte lineage specification. These pieces and additional material are available free online (www.nature.com/ni/focus/lymphocytespecification/index.html) during May 2007. Artwork by Lewis Long.

Most people infected with human immunodeficiency virus 2 (HIV-2), shown here as orange virions, do not progress to AIDS. Rowland-Jones and Whittle discuss HIV-2 pathogenesis and what it can teach about protective immunity to HIV-1 (p 329). Artwork by Lewis Long.

Minato and colleagues identify progenitors of Aire-expressing medullary thymic epithelial cells (mTECs; p. 304, see also News and Views by Hollander, p. 234). The original image (bottom) shows CD31+ endothelial cells (red), keratin 18-positive cortical TECs (blue) and keratin 5-positive mTECs (green) in the thymus of a 4-week-old mouse. Yellow indicates overlap of red and green fluorescence. Immunofluorescence by Jason Gill. Artwork by Lewis Long.

Lee and colleagues identify lymph node stromal cells that express peripheral tissue antigens and promote immunological tolerance (p 181; see also News and Views by Zehn & Bevan, p 120). The original image (bottom) shows a cross section of small intestinal villi, with intestinal epithelial cells (red) expressing the basolateral membrane protein A33 antigen and dendritic cells (green) expressing CD11c in the lamina propria. Micrograph by J.-W. Lee. Artwork by Lewis Long.

In vitro work suggests that the C-type lectin dectin-1 detects and promotes immune responses directed against β-glucans on fungal cell walls. The Brown and Iwakura groups (pp 31 and 39, News & Views by Tschopp, p 17) now show that dectin-1 is essential for controlling some fungal infections in vivo. The original photomicrograph (bottom, Taylor et al.) shows dectin-1- deficient macrophages labeled with fluorescence-tagged zymosan particles (green). Artwork by Lewis Long.