RESUMEN

gammadelta T lymphocytes in the intestinal intraepithelial layer (gammadelta IELs) are thought to contribute to immune competence, but their actual function remains poorly understood. Here we used DNA microarrays to study the gene expression profile of gammadelta IELs in a Yersinia infection system to better define their roles. To validate this approach, mesenteric lymph node CD8(+) alphabeta T cells were similarly analyzed. The transcription profiles show that, whereas lymph node CD8(+) alphabeta T cells must be activated to become cytotoxic effectors, gammadelta IELs are constitutively activated and appear to use different signaling cascades. Our data suggest that gammadelta IELs may respond efficiently to a broad range of pathological situations irrespective of their diverse T cell antigen receptor repertoire. gammadelta IELs may modulate local immune responses and participate in intestinal lipid metabolism, cholesterol homeostasis, and physiology. This study provides a strong basis for further investigations of the roles of these cells as well as mucosal immune defense in general.

Asunto(s)

RESUMEN

Cerebrospinal fluid drainage is a first line treatment used to manage severely elevated intracranial pressure (> or = 20 mm Hg) and improve outcomes in patients with acute head injury. There is no consensus regarding the optimal method of cerebrospinal fluid removal. The purpose of this investigation was to determine whether cerebrospinal fluid drainage decreases intracranial pressure and improves cerebral perfusion and to identify factors that impact treatment effectiveness. This study involved 31 severely head injured patients. Intracranial pressure and other indices of cerebral perfusion (cerebral perfusion pressure, cerebral blood flow velocity, and regional cerebral oximetry) were measured before, during, and after cerebrospinal fluid drainage. Arterial and jugular venous oxygen content was measured before and after cerebrospinal fluid drainage. Patients underwent three randomly ordered cerebrospinal fluid drainage protocols that varied in the volume of cerebrospinal fluid removed (1 mL, 2 mL, and 3 mL) for a total of 6 mL of cerebrospinal fluid removed. There was a significant change in the intracranial pressure from a mean at baseline of 26.1 mm Hg (SD = 4.4) to 22.1 mm Hg immediately after drainage. One third of patients experienced a decrease in the intracranial pressure below 20 mm Hg; in two patients the intracranial pressure dropped less than 1 mm Hg. The following factors predicted 61.5% of the variance in the responsiveness of intracranial pressure to drainage: vecuronium hypothermia, baseline cerebral perfusion pressure and acuity of illness. Cerebrospinal fluid drainage provides a transient decrease in intracranial pressure without a measurable improvement in other indices of cerebral perfusion.

Asunto(s)

RESUMEN

The progression of T cells from a quiescent or resting state to fully activated, proliferating cells is a crucial step in the initiation of an immune response. We have developed an in vitro system to study the requirements for triggering or hindering this pathway by using naive T cells derived from T-cell antigen receptor alpha beta transgenic animals and peptide-major histocompatibility (MHC) complexes coated on plates. Whereas previously stimulated T cells require only peptide-MHC complexes to produce interleukin 2 (IL-2), naive cells require at least one additional signal, which can be provided by either an anti-CD28 antibody or the protein kinase C stimulant phorbol 12-myristate 13-acetate. In contrast, the anti-CD28 antibody augments IL-2 production by primed T cells but is not required, and phorbol 12-myristate 13-acetate has no discernable effect. Thus we find that native T cells have significantly more stringent requirements for IL-2 production than primed cells and that this fits well with previous observations in other in vitro systems as well as in vivo models of autoimmunity. We also find that peptide-MHC complex stimulation of naive T cells, together with exogenous IL-2, is sufficient to convert these cells to primed T cells in vitro in 2 days, as assayed both by surface marker analysis and stimulation requirements. Taken together with the above results, this suggests that the activation of primary T cells requires at least two signals and that IL-2 produced by naive T cells in vivo may act in an autocrine fashion to allow them to proliferate and differentiate.

Asunto(s)

RESUMEN

The tetra-alanine substitution variant KHRR 296-299 AAAA of tissue-type plasminogen activator (t-PA) was previously shown to have enhanced fibrin specificity and enhanced activity in the presence of fibrin compared with the wild-type form of the molecule. The structural requirements for these alterations in enzymatic activity were investigated by constructing several amino acid substitution variants at each of the positions from 296 to 299 and evaluating their activities under a variety of conditions. Effects on plasminogen activator activity were common among the point mutants at positions 296-299; nearly all had a phenotype similar to the KHRR 296-299 AAAA variant. The greatest effects on enzymatic function were found with multiple substitution variants, but some single charge reversals and proline substitutions had substantial effects. The enhanced fibrin specificity of KHRR 296-299 AAAA t-PA results in less fibrinogenolysis than seen with wild-type t-PA. Approximately four times greater concentration of KHRR 296-299 AAAA compared with wild-type t-PA was required to consume 50% of the fibrinogen in human plasma.

Asunto(s)

Asunto(s)