Enumeration of organ-associated natural killer cells in mice: application of a new stereological method

Minireview: host defence in invasive aspergillosis

Aspergillus is a saprophytic fungus, which mainly becomes pathogenic in immunosuppressed hosts. A failure of host defences results in a diverse set of illnesses, ranging from chronic colonisation, aspergilloma, invasive disease and hypersensitivity. A key concept in immune responses to Aspergillus species is that host susceptibility determines the morphological form, antigenic structure and physical location of the fungus. Traditionally, innate immunity has been considered as a first line of defence and activates adaptive immune mechanisms by the provision of specific signals; innate and adaptive immune responses are intimately linked. The T-helper cell (TH 1) response is associated with increased production of inflammatory cytokines IFN-γ, IL-2 and IL-12 and stimulation of antifungal effector cells. Alternatively, TH 2-type responses are associated with suppression of antifungal effector cell activity, decreased production of IFN-γ and increased concentrations of IL-4 and IL-10, which promote humoral responses to Aspergillus. The host's defensive capacity is defined by the sum of resistance and tolerance. Resistance displays the ability to limit fungal burden and elimination of the pathogen, and tolerance means the ability to limit host damage caused by immune response.

Natural killer cell distribution and trafficking in human tissues

Few data are available regarding the recirculation of natural killer (NK) cells among human organs. Earlier studies have been often impaired by the use of markers then proved to be either not sufficiently specific for NK cells (e.g., CD57, CD56) or expressed only by subsets of NK cells (e.g., CD16). At the present, available data confirmed that human NK cells populate blood, lymphoid organs, lung, liver, uterus (during pregnancy), and gut. Several studies showed that NK cell homing appears to be subset-specific, as secondary lymphoid organs and probably several solid tissues are preferentially inhabited by CD56^brightCD16^neg/dull non-cytotoxic NK cells. Similar studies performed in the mouse model showed that lymph node and bone marrow are preferentially populated by CD11b^dull NK cells while blood, spleen, and lung by CD27^dull NK cells. Therefore, an important topic to be addressed in the human system is the contribution of factors that regulate NK cell tissue homing and egress, such as chemotactic receptors or homeostatic mechanisms. Here, we review the current knowledge on NK cell distribution in peripheral tissues and, based on recent acquisitions, we propose our view regarding the recirculation of NK cells in the human body.

Leukocyte compartments in the mouse lung: distinguishing between marginated, interstitial, and alveolar cells in response to injury

We developed a flow cytometry-based assay to simultaneously quantify multiple leukocyte populations in the marginated vascular, interstitial, and alveolar compartments of the mouse lung. An intravenous injection of a fluorescently labeled anti-CD45 antibody was used to label circulating and marginated vascular leukocytes. Following vascular flushing to remove non-adherent cells and collection of broncho-alveolar lavage (BAL) fluid, lungs were digested and a second fluorescent anti-CD45 antibody was added ex vivo to identify cells not located in the vascular space. In the naïve mouse lung, we found about 11 million CD45+ leukocytes, of which 87% (9.5 million) were in the vascular marginated compartment, consisting of 17% NK cells, 17% neutrophils, 57% mononuclear myeloid cells (monocytes, macrophage precursors and dendritic cells), and 10% T cells (CD4+, CD8+, and invariant NKT cells). Non-vascular compartments including the interstitial compartment contained 7.7×10(5)cells, consisting of 49% NK cells, 25% dendritic cells, and 16% other mononuclear myeloid cells. The alveolar compartment was overwhelmingly populated by macrophages (5.63×10(5)cells, or 93%). We next studied leukocyte margination and extravasation into the lung following acid injury, a model of gastric aspiration. At 1 h after injury, neutrophils were markedly elevated in the blood while all other circulating leukocytes declined by an average of 79%. At 4 h after injury, there was a peak in the numbers of marginated neutrophils, NK cells, CD4+ and CD8+ T cells and a peak in the number of alveolar NK cells. Most interstitial cells consisted of DCs, neutrophils, and CD4+ T cells, and most alveolar compartment cells consisted of macrophages, neutrophils, and NK cells. At 24 h after injury, there was a decline in the number of all marginated and interstitial leukocytes and a peak in alveolar neutrophils. In sum, we have developed a novel assay to study leukocyte margination and trafficking following pulmonary inflammation and show that marginated cells comprise a large fraction of lung leukocytes that increases shortly after lung injury. This assay may be of interest in future studies to determine if leukocytes become activated upon adherence to the endothelium, and have properties that distinguish them from interstitial and circulating cells.

Innate immunity to Aspergillus species

All humans are continuously exposed to inhaled Aspergillus conidia, yet healthy hosts clear the organism without developing disease and without the development of antibody- or cell-mediated acquired immunity to this organism. This suggests that for most healthy humans, innate immunity is sufficient to clear the organism. A failure of these defenses results in a uniquely diverse set of illnesses caused by Aspergillus species, which includes diseases caused by the colonization of the respiratory tract, invasive infection, and hypersensitivity. A key concept in immune responses to Aspergillus species is that the susceptibilities of the host determine the morphological form, antigenic structure, and physical location of the fungus. In this review, we summarize the current literature on the multiple layers of innate defenses against Aspergillus species that dictate the outcome of this host-microbe interaction.

NK cells in autoimmune disease

The role of NK cells in autoimmunity has not been extensively studied. Speaking for a disease-promoting role for NK cells in autoimmune diseases are recent results suggesting that IFN-gamma production by NK cells may help adaptive immune responses diverge in the direction of a Th1 response. NK cells may also be involved in direct killing of tissue cells, which could lead to acceleration of autoimmunity. However, NK cells have also been shown to protect from some autoimmune diseases. A possible reason for this discrepancy may lie in the capacity of NK cells also to produce Th2 cytokines, which could downregulate the Th1 responses that are common in autoimmune disorders. Thus there is at present no coherent view on the role of NK cells in autoimmunity, and more work is needed to clarify why NK cells in some cases aggravate disease and in some cases protect from disease.

Administration of BiMAb-retargeted T cells in a rat hepatic metastases colon tumour model results in T-cell tumour infiltration independent of the route of administration

In this study, cultured T cells, pre-incubated with the bispecific monoclonal antibody (BiMAb) R73IgG1 x CC52IgG1 were adoptively transferred, via systemic and regional routes, to rats bearing day 10 hepatic metastases of the CC531 adenocarcinoma of the colon to investigate the role of the route of administration in tumour infiltration by these BiMAb-retargeted effector cells. The BiMAb, directed against the T-cell receptor and the tumour-associated antigen CC52, were used to crosslink CC531 tumour cells and T cells to induce tumour cell lysis. Retargeted T cells were administered via the jugular vein, hepatic artery or the portal vein. The number of BiMAb-retargeted T cells that reached the liver tumours was independent of the route of administration. There was also no difference between the number of T cells that reached the portal tracts, central veins of parenchyma of the liver, after loco-regional or systemic administration. These findings are in contrast to the interleukin (IL)-2 activated NK (A-NK) cells biodistribution studies earlier performed in the same animal model in our laboratory. Compared with A-NK cells, a lower number of BiMAb-retargeted T cells reached the tumours, irrespective of their route of administration while for A-NK cells, there was an advantage of administration via the hepatic artery.

The effect of surgical stress and endotoxin-induced sepsis on the NK-cell activity, distribution and pulmonary clearance of YAC-1 and melanoma cells

Following surgery the activity of natural killer (NK) cells is decreased in the blood. It is possible that sepsis with release of endotoxin will further decrease the NK-cell activity. The purpose of the present study was to investigate the NK-cell cytotoxicity, the clearance in the lungs of YAC-1 and melanoma cells, as well as the distribution of NK-cells in the liver, following abdominal surgery and intraperitoneally (i.p.) administered endotoxin. Ten mice in each group were allocated to abdominal surgery, i.p. endotoxin or anaesthesia alone. Following abdominal surgery, the cytotoxicity of NK-cells isolated from the spleen was decreased and 4 h after injection the clearance of YAC-1 cells from the lungs was only 79.5+/-6.1% compared to 99.5+/-0.3% in the control group. The number of NK-cells in the liver was also significantly reduced following abdominal surgery. In contrast, i.p. endotoxin increased the activity of NK-cells by 28.5% compared to 11.8% in the control group and 8.1% in the surgery group, lowered the number of melanoma metastases in extrapulmonary organs and significantly increased the number of NK-cells in the liver. Following abdominal surgery, activity of NK-cells, pulmonary clearance and number of NK-cells in the liver were decreased. The number of NK-cells in the liver correlated with the NK-cell activity throughout the study. The increased NK-cell cytotoxicity and the increased number of NK-cells in the liver following i.p. administered endotoxin might initially be an appropriate measure against intra-abdominal infection.

Infiltration patterns of short- and long-term cultured A-NK and T-LAK cells following adoptive immunotherapy

Direct contact between lymphokine-activated killer (LAK) cells and tumour cells is believed to be imperative for initiating tumour cell lysis in vitro as well as in vivo. In order to optimize adoptive immunotherapy (AIT) it is therefore desirable to identify the LAK cell subtype, which ensures maximal infiltration of tumours as well as a substantial cytotoxic reactivity. In this report we have compared short- and long-term cultured murine adherent natural killer (A-NK) cells and mitogen-stimulated, lymphokine-activated T-killer (T-LAK) cells with respect to their proliferative potential, cytotoxicity, requirement for interleukin-2 (IL-2) and ability to infiltrate B16 pulmonary metastases following adoptive transfer. We found that short-term (5 days) cultured A-NK and T-LAK cells both showed a substantial accumulation of tumour tissues. However, A-NK cells gradually lost this ability during in vitro culture whereas T-LAK cells cultured for as long as 20 days retained their ability to infiltrate metastases as efficiently as their short-term cultured counterparts. Moreover, the low requirement of IL-2 by T-LAK cells to achieve maximal infiltration of tumours sharply contrasted with the excessive doses necessary to ensure maximal infiltration by A-NK cells. In conclusion, these data demonstrate that short-term cultured LAK cells of both NK- and T-cell origin are able to infiltrate B16 pulmonary metastases effectively. Importantly, the T cells retain this ability for a considerably longer time and require much less IL-2 support than do A-NK cells, making T-LAK cells attractive for AIT.

Regional administration of natural killer cells in a rat hepatic metastasis model results in better tumor infiltration and anti-tumor response than systemic administration

A syngeneic rat liver metastasis model, the CC531 colon carcinoma cell line in Wag rats, was used to study the homing properties and anti-tumor effects of adoptively transferred, interleukin-2 (IL-2)-activated, cultured natural killer (A-NK) cells. To identify the route of administration that gives the highest tumor infiltration, 1.5 x 10(8) A-NK cells were dyed with fluorescent rhodamine and injected via 4 different routes into rats, bearing subcapsularly induced (day 10) liver metastases. The routes chosen were: jugular vein, portal vein, hepatic artery and directly into the peritoneal cavity (i.p). The rats were sacrificed 20 hr after administration of A-NK cells. The highest (p < 0.05) infiltration of tumors by A-NK cells was found both at the tumor border and in the tumor center after injection via the hepatic artery: 65 +/- 7 A-NK cells/mm2 at the tumor border and 26 +/- 14 A-NK cells/mm2 in the center of the tumor (jugular vein infusion: 32 +/- 10 and 9 +/- 5 A-NK cells/mm2, respectively; portal vein infusion: 36 +/- 13 and 7 +/- 4 A-NK cells/mm2, respectively). No A-NK cells were detected in the liver after i.p. injection. Rats bearing day 5 tumors were injected with 1.5 x 10(8) A-NK cells via the hepatic artery or via the jugular vein (n = 5 and n = 6 respectively). Regional administration of A-NK cells via the hepatic artery resulted in a significant (p < 0.05) lower weight (35 +/- 23 mg) of tumors than did systemic administration (70 +/- 10 mg). Our results suggest that both the level of tumor infiltration by adoptively transferred A-NK cells and the therapeutic outcome depend on the route of administration.

Distribution of leukocytes in the epithelium and interstitium of four regions of the Lewis rat epididymis

BACKGROUND

Leukocytes expressing different surface markers were studied in four regions of the epididymis of Lewis rats. Cells resembling lymphocytes or monocytes had been described in the epididymis, but previous studies differed as to their nature and immunologic significance.

METHODS

Frozen sections were immunocytochemically stained with monoclonal antibodies W3/25, OX-8, OX-42, and RLN-9D3, which are directed toward markers on CD4+ cells, CD8+ cells, macrophages, and B lymphocytes, respectively. The concentration of stained cells in the epithelium and interstitial tissue of the initial segment, caput, proximal cauda, and distal cauda regions was determined by a procedure based on the optical disector method.

RESULTS

CD4+ leukocytes were present in greater concentration than CD8+ cells or macrophages in both the epithelium and interstitial tissue of all four regions. In the epithelium, the concentration of CD8+ leukocytes was greater than that of macrophages in the initial segment, caput, and distal cauda. In the interstitium, however, the concentration of macrophages exceeded that of CD8+ cells in both parts of the cauda. Macrophages and T lymphocytes were generally present in greater concentrations in the interstitium than in the epithelium, especially in the more proximal parts of the epididymis. In contrast to T cells, B lymphocytes were not detected in the interstitium or epithelium of any of part of the epididymis, despite prominent staining of B cells in other locations.

CONCLUSIONS

The epididymal epithelium of the Lewis rat contains many T lymphocytes, which may correspond to 'halo' cells. CD4+ leukocytes predominate in all regions of the epididymis. The interstitium may function as a reservoir of leukocytes for the epithelial compartment. The epididymis is not normally a site for local immunoglobulin synthesis.

Kinetics and dose dependence of macrophage colony-stimulating factor-induced proliferation and activation of murine mononuclear phagocytes in situ: differences between lungs, liver, and spleen

Alveolar macrophages (AM) play an important role in antimicrobial defense mechanisms of the lung. It therefore seems reasonable to use macrophage colony-stimulating factor (M-CSF) to enhance local resistance mechanisms. However, little is known about the in vivo activity of M-CSF on macrophages in various organs. We determined the effect of a single subcutaneous dose of M-CSF (10, 50, 100, and 500 ng, respectively) on the number and functional status of AM as well as of macrophages in liver and spleen of mice. Organs were investigated immunohistochemically on days 1 and 3 after injection using monoclonal antibodies specific for F4/80, Ia antigen, and MAC-1. We found a significant increase in the number of F4/80+ AM, Kupffer cells, and splenic macrophages reaching its maximum 24 h after injection of low doses (10 and 50 ng per mouse, respectively) of M-CSF and decreasing to a level seen in untreated mice at 72 h after M-CSF in liver and spleen, whereas at a dose of 50 ng per mouse the number of AM remained high. In contrast, the numbers of AM, Kupffer cells, and splenic macrophages did not increase significantly when high doses were used (500 ng). The expression of Ia antigen and MAC-1 was increased on macrophages in the spleen but not on AM or Kupffer cells. TNF-alpha was elevated in bronchoalveolar (BAL) fluid after 3 h and IL-6 at 6, 12, and 24 h after M-CSF injection in dose-dependent manner. Nitric oxide production was not increased after injection of M-CSF. Our results point to regional differences in the response of macrophages to M-CSF. These may caused by differences in the M-CSF-induced production of TNF-alpha and IL-6. These findings may be important for the therapeutic use of M-CSF in microbial infections.

The infiltration of experimentally induced lung metastases of colon carcinoma CC531 by adoptively transferred interleukin-2-activated natural killer cells in Wag rats

The number of IL-2-activated natural killer (A-NK) cells reaching the tumor site in vivo may be crucial for their anti-tumor effect following adoptive immunotherapy. We investigated in a syngeneic rat model the infiltration of established lung metastases by adoptively transferred A-NK cells. The Wag rat colon carcinoma CC531 was injected via a tail vein to induce pulmonary metastases. Syngeneic A-NK cells were labeled with the fluorescent dye rhodamine (TRITC) and next injected via a tail vein in rats bearing day-12 lung tumors. The number of A-NK cells in tumor and in normal tissue per rat was counted in sections after administration of A-NK cells. At all time points tested, a significant linear relationship between the cross-section area of the tumor and the number of infiltrating cells was observed, but small tumor areas became fully infiltrated earlier than larger areas. At 24 hr after injection, approximately 10% of the injected cells were found in the tumor tissue and the average A-NK-cell-to-tumor-cell ratio was estimated to be 1:3. A-NK cells were found in the liver too, although the number of cells per mm2 tissue was low compared with the pulmonary tumor tissue. Very low numbers of A-NK cells were found in kidney, adrenal gland, spleen, and blood. We conclude that, in this syngeneic rat model, adoptively transferred A-NK cells are able to find and specifically infiltrate pulmonary metastases in a time-dependent fashion.