Interleukin-2 (IL-2) signaling requires the dimerization of the IL-2 receptor beta.(IL-2R beta) and common gamma (gamma c) chains. Mutations of gamma c can result in X-linked severe combined immunodeficiency (XSCID). IL-2, IL-4, IL-7 (whose receptors are known to contain gamma c), and IL-9 (whose receptor is shown here to contain gamma c) induced the tyrosine phosphorylation and activation of the Janus family tyrosine kinases Jak1 and Jak3. Jak1 and Jak3 associated with IL-2R beta and gamma c, respectively; IL-2 induced Jak3-IL-2R beta and increased Jak3-gamma c associations. Truncations of gamma c, and a gamma c, point mutation causing moderate X-linked combined immunodeficiency (XCID), decreased gamma c-Jak3 association. Thus, gamma c mutations in at least some XSCID and XCID patients prevent normal Jak3 activation, suggesting that mutations of Jak3 may result in an XSCID-like phenotype.

The lymphocyte function-associated 1 (LFA-1), ~ Mac-l, and p150,95 molecules constitute a family of structurally and functionally related, high molecular weight, human leukocyte surface glycoproteins (1). Each molecule contains an a and a 3 subunit noncovalently associated in an al31 structure. The 3 subunits of Mr 95,000 in each of these three molecules are identical. The molecules are distinguished by their a subunits, which have different isoelectric points, molecular weights, and cell distributions, and are immunologically non-cross-reactive. The relative molecular weights of the Mac-l, LFA-1, and p150,95 a subunits are 165,000, 177,000, and 150,000 for aM, aL, and aX, respectively. This glycoprotein family is conserved in mouse and human (1, 2). In both species, the a and 3 subunits of each molecule are biosynthesized as separate a' and ~' intracellular precursors (1, 3). The precursors associate into a'~' complexes, are processed to the mature a3 form, and then transported to the cell surface. The murine aM and aL subunits have 33% amino acid sequence homology with one another. 2 Such homology suggests that a primordial a chain gene duplication event(s) led to the evolution of this glycoprotein family.The LFA-1 and Mac-1 molecules contribute to multiple types of leukocyte adhesion reactions. The LFA-1 molecule participates in the formation of adhesions between effector and target cells in cytolytic T lymphocyte-mediated killing and in natural killing, as shown by monoclonal antibody (mAb) blocking experiments (4-6). LFA-1 also participates in T helper cell responses, and its distribution on B cells, granulocytes, and monocytes suggests it may function in adhesion of these cells as well (7). Mac-1 has been defined (8) by mAb as a mouse differentiation antigen present on myeloid and absent on lymphoid cells. Subse-

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This animal model closely resembles hyperdynamic sepsis in humans and may be of great value for studies of sepsis with smoke inhalation.

Patients with severe burn and/or smoke inhalation injury suffer both systemic and pulmonary vascular hyperpermeability. We hypothesized that nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) plays a role in the changes in microvascular permeability seen with this injury. To test the hypothesis, we administered mercaptoethylguanidine (MEG), a selective iNOS inhibitor, to conscious sheep subjected to a combined smoke inhalation and third-degree burn injury to 40% of total body surface area. The sheep were surgically prepared for chronic study with lung and prefemoral lymph fistulas in order to estimate microvascular permeability. Both the groups and a control group of animals showed an increase in iNOS protein and message in their lungs. The control animals showed significant increases in either plasma or lymph NO2-/NO3- (NOx) concentration at 24 h after injury, with associated cardiac depression and hemoconcentration. The airway epithelium stained for nitrotyrosine. In the treatment group, NOx did not increase significantly in plasma or lymph throughout the experiment, there was no nitrotyrosine staining, hemodynamic depression was not observed, and the fluid requirement was significantly less than in the control group. Changes in pulmonary microvascular permeability were significantly suppressed by inhibition of iNOS. However, there was no significant difference between the two study groups in the microvascular permeability of burned tissue. These data suggest that NO produced by iNOS plays an important role in the changes in systemic and pulmonary microvascular permeability in combined smoke inhalation/third-degree burn injury, but does not affect the vascular permeability of third-degree-burned tissue in this type of injury.

The clinical, histopathologic and functional consequences of the genetic deficiency of leukocyte Mac‐1, LFA‐1 and p150,95 were assessed among (1) three affected patients, (2) heterozygotes and (3) unaffected individuals among two generations of a single kindred. Longitudinal assessments of this family afforded the unique opportunity to characterize the natural history of severe periodontal manifestations associated with this disorder. Features uniformly observed among each patient included recurrent, necrotic soft tissue infections, impaired pus formation, delayed wound healing, constant granulocytosis, severe abnormalities of adhesion‐dependent granulocyte functions and a profound deficiency (3%–6% of normal) of Mac‐1 glycoproteins on granulocyte surfaces. Characteristic features of generalized prepubertal periodontitis including rapidly progressive alveolar bone loss affecting the primary and permanent dentitions (leading to premature tooth loss), recession, clefting and migration in association with intense gingival inflammation were uniformly observed. Biopsies of inflamed periodontal tissues in these individuals demonstrated dense infiltrates of mononuclear leukocytes but a striking absence of extravascular neutrophil granulocytes. Heterozygous family members demonstrated approximately half normal Mac‐1 protein expression but no susceptibility to systemic infections and normal, adhesion‐dependent leukocyte functions. Prepubescent heterozygotes demonstrated no periodontal manifestations but a 31‐year‐old heterozygous female exhibited clinical and radiographic features typical of postjuvenile periodontitis. The profound periodontal manifestations recognized in this clinical‐pathologic model emphasize the physiologic importance of leukocyte adhesion reactions in defense of the periodontium and further suggest a possible pathologic role for Mac‐1 proteins in other forms of early‐onset periodontitis.

Since activated macrophages and cytokines are found in human milk (HM), a flow cytometry study was conducted to determine whether T cells in HM display phenotypic markers of recent or previous activation. HM was collected during the first 3 d of lactation. The Paint-a-Gate program was used to optimize gating on the lymphocyte population. A mean & 1 SD of 4 & 3% of total HM leukocytes were lymphocytes and 96 f 3% were macrophages and granulocytes (N = 33 subjects). HM lymphocyte populations were further analyzed in five subjects. T cells (CD3+) represented 83 f 11% and B cells (CD19') were 6 & 4% of HM lymphocytes. The mean CDWCDB ratio of T cells in HM was 0.88 (range 0.40-1.25). This ratio was significantly decreased compared to the peripheral blood (PB) of control adults (P < 0.02) and postpartum women (P < 0.021, due mostly to a significant increase in CD8+ CD3+ cells in HM compared to the PB of control adults (P < 0.002) and postpartum women (P < 0.05). T cells bearing markers of recent activation were significantly increased in HM compared to the PB of control adults: 85 f 7% of CD3+ cells in HM were HLA-DR+ (controls, 10 f : 4%; P < 0.001), and 15 k 6% of CD3+ cells in HM were IL-2R+ (controls, 6 f 2%; P < 0.001). Subpopulations of CD4+ and CD8+ cells in HM defined by the T200 isoforms CD45RA and CD45RO were markedly altered compared to PB, indicating a striking shift from virginal to antigen-primed (memory) T cells in HM and suggesting certain functional capacities for these cells. Virtually all CD4+ cells (99.8 2 0.4%) and 92 f 5% of CDB+ cells in HM were CD45RO+ (vs. 71 f 12% and 50 f lo%, respectively, in the PB of postpartum women; P < 0.001). CD4+ and CD8+ cells expressing CD45RA were correspondingly markedly reduced (P < 0.001). This phenotypic pattern of T cells in HM may result from T cell activating substances in HM and/or selective homing of T cells to the breast. Conversely, activated T cells in HM may be responsible for cytokines in HM. These activated and memory T cell populations may be transferred to the infant via breastfeeding.Key terms: Human milk immunology, T lymphocyte subsets, flow cytometry, markers of activation, leukocyte common antigen isoforms It has been known for some years that leukocytes are part of the immunologic system in human milk (HM) (42,121. About 3 million leukocytes are found in each milliliter of HM produced during the first few days postpartum, and the principal types of leukocytes found in HM during that period are neutrophils (40-60%), macrophages (30-50%), and lymphocytes (5-9%). T cells comprise 60-73% of HM lymphocytes based on the capacity to form rosettes with sheep erythrocytes [12,34], and the thermostability of these rosettes suggests that HM T cells are activated [341. The

The goals of this study were (i) to compare the degree and (ii) temporal changes in airway obstruction in sheep with pulmonary injury induced by smoke inhalation and/or burn; (iii) to qualitatively assess the cellular and mucous content of obstructive material; and (iv) to statistically assess a possible relationship between the degree of airway obstruction and pulmonary dysfunction. Using masked histologic slides, we estimated the degree of luminal obstruction in all cross-sectioned airways. The mean degree of bronchial, bronchiolar, and terminal bronchiolar obstruction was significantly greater in animals with smoke injury alone or combined smoke inhalation and burn (S+B) injury, compared with animals with burn injury alone or uninjured animals (P < 0.05). In S+B animals, the degree of bronchial obstruction was maximal at 24 h, with a progressive decrease over 72 h. In contrast, the degree of bronchiolar obstruction increased over time. Qualitatively, bronchial casts were largely composed of mucus at early times after injury, whereas neutrophils were the principal component of bronchiolar obstructive material. Localization of specific mucin subtypes in S+B tissues suggests that increasing bronchiolar obstruction is derived, in part, from upper airway material. Multiple linear regression analysis of airway obstruction scores compared with PaO2/FIO2 values showed a correlation coefficient of r = 0.76, with bronchial and bronchiolar scores predictive of PaO2/FIO2, (P < 0.05). These results suggest that strategies to remove or decrease formation of upper airway obstructive material may reduce its deposition into small airways and parenchyma and may improve respiratory function in victims of smoke inhalation injury.