Effect of space flight on cytokine production and other immunologic parameters of rhesus monkeys.

During a recent flight of a Russian satellite (Cosmos #2229), initial experiments examining the effects of space flight on immunologic responses of rhesus monkeys were performed to gain insight into the effect of space flight on resistance to infection. Experiments were performed on tissue samples taken from the monkeys before and immediately after flight. Additional samples were obtained approximately 1 month after flight for a postflight restraint study. Two types of experiments were carried out throughout this study. The first experiment determined the ability of leukocytes to produce interleukin-1 and to express interleukin-2 receptors. The second experiment examined the responsiveness of rhesus bone marrow cells to recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF). Human reagents that cross-reacted with monkey tissue were utilized for the bulk of the studies. Results from both studies indicated that there were changes in immunologic function attributable to space flight. Interleukin-1 production and the expression of interleukin-2 receptors was decreased after space flight. Bone marrow cells from flight monkeys showed a significant decrease in their response to GM-CSF compared with the response of bone marrow cells from nonflight control monkeys. These results suggest that the rhesus monkey may be a useful surrogate for humans in future studies that examine the effect of space flight on immune response, particularly when conditions do not readily permit human study.

Spaceflight alters immune cell function and distribution.

Experiments were carried out aboard COSMOS 2044 to determine the effects of spaceflight on immunologically important cell function and distribution. Control groups included vivarium, synchronous, and antiorthostatically suspended rats. In one experiment, rat bone marrow cells were examined in Moscow, for their response to recombinant murine granulocyte/monocyte colony-stimulating factor (GM-CSF). In another experiment, rat spleen and bone marrow cells were stained in Moscow with a variety of antibodies directed against cell surface antigenic markers. These cells were preserved and shipped to the United States for analysis on a flow cytometer. Bone marrow cells from flown and suspended rats showed a decreased response to granulocyte/monocyte colony-stimulating factor compared with bone marrow cells from control rats. Of the spleen cell subpopulations examined from flown rats, only those cells expressing markers for suppressor-cytotoxic T- and helper T-cells showed an increased percentage of stained cells. Bone marrow cells showed an increase in the percentage of cells expressing markers for helper T-cells in the myelogenous population and increased percentages of anti-asialo granulocyte/monocyte-1-bearing interleukin-2 receptor-bearing pan T- and helper T-cells in the lymphocytic population. Cell populations from rats suspended antiorthostatically did not follow the same pattern of distribution of leukocytes as cell populations for flown rats. The results from COSMOS 2044 are similar, but not identical, to earlier results from COSMOS 1887 and confirm that spaceflight can have profound effects on immune system components and activities.

Effect of spaceflight on natural killer cell activity.

The effects of spaceflight on immune cell function were determined in rats flown on COSMOS 2044. Control groups included vivarium, synchronous, and antiorthostatically suspended rats. The ability of natural killer cells to lyse two different target cell lines was determined. Spleen and bone marrow cells obtained from flight rats showed significantly inhibited cytotoxicity for YAC-1 target cells compared with cells from synchronous control rats. This could have been due to exposure of the rats to microgravity. Antiorthostatic suspension did not affect the level of cytotoxicity from spleen cells of suspended rats for YAC-1 cells. On the other hand, cells from rats flown in space showed no significant differences from vivarium and synchronous control rats in cytotoxicity for K-562 target cells. Binding of natural killer cells to K-562 target cells was unaffected by spaceflight. Antiorthostatic suspension resulted in higher levels of cytotoxicity from spleen cells for 51Cr-labeled K-562 cells. The results indicate differential effects of spaceflight on function of natural killer cells. This shows that spaceflight has selective effects on the immune response.

Adenovirus 21 infection in an isolated antarctic station: transmission of the virus and susceptibility of the population.

Natural dissemination of viral respiratory illness to susceptible men may occur with surprising difficulty. This was especially evident during a 1977 outbreak of adenovirus type 21 (Ad-21) at McMurdo Station, a US research base in Antarctica. The unique circumstances at McMurdo allowed 125 men from the US to join and intermingle with 75 men who had wintered for 6 months in complete isolation. For an additional 5-week (September 2 to October 4, 1977) isolation period, respiratory illness etiology and transmission were monitored in the combined population. A total of 89% of the population was susceptible (neutralizing antibody titer, less than 1:3) to Ad-21 but only 15.0% were infected. Illness spread very slowly (1.5 cases/100 persons/week) with no epidemic peak and was much less severe than Ad-21 outbreaks in other settings. The incidence of infection (17.3%) and illness (9.6%) was low even in men who had wintered over, with values very similar to those of the newcomers (13.9% and 8.9%, respectively). Thus, despite a harsh environment and frequent prolonged gatherings of susceptible personnel, even a respiratory virus type with known epidemic potential was surprisingly difficult to transmit.

Effects of spaceflight on levels and activity of immune cells.

Experiments were carried out on cells from rats that had been flown on Soviet Biosputnik Cosmos 1887 to explore the effects of spaceflight on immune responses. Rat bone marrow cells were examined for their response to colony stimulating factor-M. Rat spleen and bone marrow cells were stained with antibodies directed against cell surface antigenic markers. The results of the studies indicate that bone marrow cells from flown rats showed a decreased response to colony stimulating factor. There was a higher percentage of spleen cells from flown rats staining positively for pan-T-cell, suppressor-T-cell and interleukin-2 receptor cell surface antigens. A small increase in the percentage of cells staining positively for helper-T-cell antigens was also noted. In addition, a higher percentage of cells that appeared to be part of the myelogenous population of bone marrow cells from flown rats stained positively for surface immunoglobulin.

Rhinovirus infections in an isolated antarctic station. Transmission of the viruses and susceptibility of the population.

It is commonly believed that living in polar isolation causes high susceptibility to respiratory illness. At McMurdo Station, a US research base in Antarctica, we tested this belief by comparing, over 36 days (August 31-October 5, 1976), the incidence and severity of respiratory illness in 64 men finishing six months isolation and in 136 men just arrived from the United States. The colds in the two intermingled populations were essentially equivalent. Forty-three per cent of the newcomers and 39% of the wintering group reported colds; symptoms and duration were nearly identical between the two populations. Movement of the colds was slow. The newcomers brought in 31 colds; subsequently, only 52 evenly spaced illnesses arose. Incidence of respiratory illness was twice higher in the smaller living units than in the spacious main dormitory. Two nontypable rhinoviruses, McMurdo 4 and McMurdo 88, were brought in by the new population and were the only viruses isolated. Only McMurdo 88 spread, although more than 65% of the men were antibody-free (less than 1:3) to either agent. McMurdo 88 caused an estimated 60% of antarctic-contracted colds. In brief, this isolated polar group was not especially susceptible to respiratory illness, and virus movement through the group was deliberate.

Inhibited interferon production after space flight.

Several studies have been performed in our laboratories indicating that interferon production may be impaired in rodents after space flight. Using an antiorthostatic suspension model that simulates some of the effects of microgravity seen during space flight, we have shown that interferon-alpha/beta production was inhibited. The inhibition was not due solely to the stress of suspension. The inhibited interferon production was transient, as suspended animals returned to normal caging recovered the ability to produce interferon. Antiorthostatic suspension of mice also resulted in a loss of resistance to infection with the diabetogenic strain of encephalomyocarditis virus, which correlated with the drop in interferon production. In rats flown in US Space Shuttle mission SL-3, interferon-gamma production was inhibited severely when spleen cells were challenged with concanavalin-A upon return to earth. In contrast, interleukin-3 production by these cells was normal. These results suggest that immune responses may be altered after antiorthostatic modeling or space flight, and the resistance to viral infections may be especially affected.

Inhibited interferon-gamma but normal interleukin-3 production from rats flown on the space shuttle.

Rats were flown on Space Shuttle SL-3 for 1 week. When spleen cells were removed from these rats and challenged with concanavalin-A, interferon-gamma production was severely inhibited, while interleukin-3 production was unaffected compared to ground-based control rats. These data indicate that there is a defect in interferon-gamma production in rats that have been exposed to spaceflight. This defect could contribute to, and be one reason for, immunosuppression observed after spaceflight.

Knowledge-based landmarking of cephalograms.

Orthodontists have defined a certain number of characteristic points, or landmarks, on X-ray images of the human skull which are used to study growth or as a diagnostic aid. This work presents the first step toward an automatic extraction of these points. They are defined with respect to particular lines which are retrieved first. The original image is preprocessed with a prefiltering operator (median filter) followed by an edge detector (Mero-Vassy operator). A knowledge-based line-following algorithm is subsequently applied, involving a production system with organized sets of rules and a simple interpreter. The a priori knowledge implemented in the algorithm must take into account the fact that the lines represent biological shapes and can vary considerably from one patient to the next. The performance of the algorithm is judged with the help of objective quality criteria. Determination of the exact shapes of the lines allows the computation of the positions of the landmarks.

Dimethyl sulfoxide: lack of suppression of the humoral immune response in mice.

Mice were injected intraperitoneally (i.p.) with 100% dimethyl sulfoxide (DMSO) or sterile saline (controls) for 36 days. The mice received 0.05 ml daily for one week, 0.025 ml every other day for the second week (because the DMSO-treated mice appeared weak), and 0.05 ml daily for 3 more weeks. All mice were immunized twice with sheep red blood cells (days 13 and 24), and bled twice by caudal incision (days 20 and 29). Hematocrits were significantly decreased (P less than or equal to 0.002) but still within the normal range. The primary and secondary antibody response to sheep red blood cells (SRBC), leukocyte counts, body weight, and the size of the heart, lungs, spleen, thymus, and kidneys were not affected. DMSO treatment resulted in significant liver enlargement (P = 0.02). It is concluded that this dose of DMSO is not deleterious to the humoral immune response in mice responding to a new antigen.

Methyldopa: effects on the murine immune system.

Mice were treated for 7 weeks with doses of methyldopa somewhat exceeding those given to man, and mixed immunotoxic effects were observed. Daily subcutaneous injections of 5 mg (in 0.1 ml) methyldopa or saline (0.1 ml) did not generally alter body weights, except on day 19, when the methyldopa-treated mice weighed significantly less. During treatment, all mice were immunized twice with sheep red blood cells (SRBC) and bled four times. Anti-SRBC titers were not affected by methyldopa treatment, but leukocyte counts were dramatically decreased, and hematocrits to a lesser degree. Although in methyldopa-treated mice spleen and kidneys were increased in size, liver, lung, heart, and thymus size was not affected. These results are discussed in the context of other studies on the mode of action of methyldopa in eliciting an autoimmune anemia in man treated therapeutically with this drug.

Effect of antiorthostatic suspension on interferon-alpha/beta production by the mouse.

Mice were suspended in a model that simulates weightlessness that occurs during prolonged space flight. After 1 and 2 weeks of suspension in an antiorthostatic (head-down tilt) position, the mice were challenged with polyriboinosinic-polyribocytidylic acid to induce interferon-alpha/beta. Interferon production was severely reduced in mice that had been suspended. When mice were allowed to recover in cages for a week following removal from suspension, they recovered their full interferon-production capacity. Mice suspended in an orthostatic (horizontal) position did not have their interferon production capabilities affected, which indicates that stress per se was not a major component in the effects of antiorthostatic suspension on interferon induction.

A suspension model for hypokinetic/hypodynamic and antiorthostatic responses in the mouse.

Hypokinetic/hypodynamic and antiorthostatic responses to weightlessness and bedrest were simulated in mice using a suspension technique. Animals were suspended for 1 or 2 weeks in an antiorthostatic posture and positioned to permit freedom of movement but eliminate load bearing by the hindlimbs. Suspended mice exhibited reduced food and water intakes and rapid 10% decrease in body weight to a level which was maintained for the remainder of the suspension period. Diuresis was evident in suspended mice, but the natriuresis and kaliuresis previously observed in the suspended rat were not evident. Differential hindlimb muscle atrophy (soleus greater than plantaris = gastrocnemius greater than EDL) and increased excretion of urea and ammonia were also noted in suspended mice. Postsuspension recovery studies indicated that the recovery process was highly effective. These results document specific responses to hypokinesia/hypodynamia and antiorthostasis in the mouse and demonstrate similarities in the responses of mice and rats to suspension. These studies expand the utility of the suspension model and suggest that the mouse may be useful in future studies simulating both weightlessness and bedrest.

Effect of ethanol on the immune system in mice.

Mice were injected with ethanol (2.5 g/kg body wt., i.p.) 1-3 times daily for 17 days or 3 times daily for 49 days. The primary and secondary antibody titers to sheep red blood cells were determined. In addition, microhematocrits, white blood cell counts, white blood cell differential counts, and organ-to-body-weight ratios were determined. Despite continuous large doses of ethanol, the ethanol-treated mice responded as well as saline-treated controls in all parameters tested. The results of this study are discussed in the context of other studies on the effects of ethanol on the immune system.

Effect of a simulated weightlessness model on the production of rat interferon.

A rat model simulating some aspects of weightlessness was used to determine whether simulated weightlessness might alter interferon production. The optimum time for in-vivo induction of alpha/beta interferon (alpha/beta-IFN) by polyriboinosinic-polyribocytidylic acid was determined to be four hours in normal, mature rats. Rats suspended in the model for two weeks were injected with polyriboinosinic-polyribocytidylic acid and bled four hours later. A dramatic decrease (80%) in alpha/beta-IFN production was observed in those animals exposed to simulated weightlessness as compared to control rats. These data suggest that weightlessness may alter certain immunological functions.

Type II interferon induction and passive transfer depress the murine cytochrome P-450 drug metabolism system.

Induction of type II interferon by sensitization of mice with Mycobacterium tuberculosis strain BCG and challenge with tuberculin resulted in a depression of the cytochrome P-450 drug metabolism system of the liver. The degree of depression was significantly greater than in mice that were only sensitized to BCG. Cytochrome b5 levels were not affected. In addition, the level of the depression of the cytochrome P-450 system correlated with the levels of type II interferon induced. Passive transfer of exogenous type II interferon preparations also significantly depressed the cytochrome P-450 system. Passive transfer of mock interferon or of normal serum had no effect.