The respiratory tract has an approximate surface area of 70 m2 in adult humans, which is in virtually direct contact with the outside environment. It contains a uniquely rich vascular bed containing a large pool of marginated T cells, and harbours a layer of single-cell-thick epithelial tissue through which re-oxygenation of blood must occur uninterrupted for survival. It is therefore not surprising that the respiratory tract is never more than a short step away from disaster. We have only a partial understanding of how immunological homeostasis is maintained in these tissues, but it is becoming clear that the immune system has evolved a range of specific mechanisms to deal with the unique problems encountered in this specialized microenvironment.

APCs, including dendritic cells (DC), are central to Ag surveillance in the respiratory tract (RT). Research in this area is dominated by mouse studies on purportedly representative RT-APC populations derived from whole-lung digests, comprising mainly parenchymal tissue. Our recent rat studies identified major functional differences between DC populations from airway mucosal vs parenchymal tissue, thus seriously questioning the validity of this approach. We addressed this issue for the first time in the mouse by separately characterizing RT-APC populations from these two different RT compartments. CD11chigh myeloid DC (mDC) and B cells were common to both locations, whereas a short-lived CD11cneg mDC was unique to airway mucosa and long-lived CD11chigh macrophage and rapid-turnover multipotential precursor populations were predominantly confined to the lung parenchyma. Airway mucosal mDC were more endocytic and presented peptide to naive CD4+ T cells more efficiently than their lung counterparts. However, mDC from neither site could present whole protein without further maturation in vitro, or following trafficking to lymph nodes in vivo, indicating a novel mechanism whereby RT-DC function is regulated at the level of protein processing but not peptide loading for naive T cell activation.

On the basis of the positions of behaviors relative to one another in the interpersonal circle, the principles of complementarity and anticomplementarity specify how people's behaviors influence one another in interpersonal interactions. Pairs of undergraduate women (1 subject, N = 80, and 1 confederate) collaborated for 16 min to create and agree on stories for two pictures. Confederates performed scripted roles that emphasized one of eight interpersonal behaviors. Behaviors were coded into eight categories, and the relative effect of each confederate behavior on each subject behavior was determined. Using the geometric properties of the interpersonal circle, vectors were calculated that identified the relative impact of each confederate stimulus behavior on the overall pattern of subject responses. Results were consistent with the dynamic relations among interpersonal behaviors that complementarity and anticomplementarity propose and demonstrated that how a person behaves toward another systematically and profoundly affects how the other behaves toward the person.