Migration of so-called naive and memory T lymphocytes from blood to lymph in the rat. The influence of IFN-gamma on the circulation pattern

It has been suggested that naive T lymphocytes migrate directly from the blood into the lymph nodes, whereas memory T lymphocytes arrive via the afferent lymphatics. However, these routes were defined indirectly by determining only the frequencies of naive and memory T lymphocytes in the afferent and efferent lymph of sheep. In this study naive (CD45RC+) and memory (CD45RC-) CD4+ lymphocytes obtained by thoracic duct cannulation of the rat were injected i.v. and their reappearance in the thoracic duct lymph (efferent lymph) was monitored in absolute numbers over 5 days. In addition, it was investigated whether continuous application of IFN-gamma influences the migration of the two subsets differently. After i.v. injection both naive and memory T lymphocytes returned to the thoracic duct in considerable numbers and with similar kinetic patterns. Interestingly, within 5 days at least 25% of memory phenotype lymphocytes converted to naive phenotype lymphocytes. When naive and memory T lymphocytes were injected in animals receiving a continuous IFN-gamma infusion, only the reappearance of the naive T lymphocytes but not that of memory T lymphocytes in the thoracic duct lymph was reduced. Thus, by investigating the migration of labeled lymphocytes, data were obtained that contradict conclusions drawn by analyzing preferential accumulation of lymphocyte subsets only. Our results suggest that in unstimulated animals naive and memory thoracic duct lymphocytes migrate at a similar tempo and to a comparable extent from the blood via the lymph node into the efferent lymph. IFN-gamma only influences the traffic of naive lymphocytes, indicating that the migration of the two populations is regulated by different mechanisms.

Migration of so-called naive and memory T lymphocytes from blood to lymph in the rat. The influence of IFN-gamma on the circulation pattern

It has been suggested that naive T lymphocytes migrate directly from the blood into the lymph nodes, whereas memory T lymphocytes arrive via the afferent lymphatics. However, these routes were defined indirectly by determining only the frequencies of naive and memory T lymphocytes in the afferent and efferent lymph of sheep. In this study naive (CD45RC+) and memory (CD45RC-) CD4+ lymphocytes obtained by thoracic duct cannulation of the rat were injected i.v. and their reappearance in the thoracic duct lymph (efferent lymph) was monitored in absolute numbers over 5 days. In addition, it was investigated whether continuous application of IFN-gamma influences the migration of the two subsets differently. After i.v. injection both naive and memory T lymphocytes returned to the thoracic duct in considerable numbers and with similar kinetic patterns. Interestingly, within 5 days at least 25% of memory phenotype lymphocytes converted to naive phenotype lymphocytes. When naive and memory T lymphocytes were injected in animals receiving a continuous IFN-gamma infusion, only the reappearance of the naive T lymphocytes but not that of memory T lymphocytes in the thoracic duct lymph was reduced. Thus, by investigating the migration of labeled lymphocytes, data were obtained that contradict conclusions drawn by analyzing preferential accumulation of lymphocyte subsets only. Our results suggest that in unstimulated animals naive and memory thoracic duct lymphocytes migrate at a similar tempo and to a comparable extent from the blood via the lymph node into the efferent lymph. IFN-gamma only influences the traffic of naive lymphocytes, indicating that the migration of the two populations is regulated by different mechanisms.

IFN-gamma influences the migration of thoracic duct B and T lymphocyte subsets in vivo. Random increase in disappearance from the blood and differential decrease in reappearance in the lymph

Thoracic duct lymphocytes (TDL) continuously patrol through the body, facilitating immune responses at most sites. IFN-gamma might regulate immune responses by influencing the migration of TDL. Therefore, it was investigated in vivo whether IFN-gamma affects the migration of thoracic duct B, T, CD4+, and CD8+ lymphocytes from blood to lymph. Labeled TDL were injected i.v. into rats continuously receiving IFN-gamma via a central venous catheter. The numbers of B, T, CD4+, and CD8+ lymphocytes were determined in blood and thoracic duct lymph for 120 h. IFN-gamma increased the disappearance of TDL from the blood to a similar extent in all subsets. In contrast, the reappearance of B and T lymphocyte subsets in the lymph was decreased: B lymphocytes were affected significantly more than T lymphocytes, whereas CD4+ and CD8+ lymphocytes were affected to a similar extent. Our study suggests that differential retention within the tissue rather than preferential immigration into the tissue creates a microenvironment with a distinct composition of lymphocyte subsets.

IFN-gamma influences the migration of thoracic duct B and T lymphocyte subsets in vivo. Random increase in disappearance from the blood and differential decrease in reappearance in the lymph

Thoracic duct lymphocytes (TDL) continuously patrol through the body, facilitating immune responses at most sites. IFN-gamma might regulate immune responses by influencing the migration of TDL. Therefore, it was investigated in vivo whether IFN-gamma affects the migration of thoracic duct B, T, CD4+, and CD8+ lymphocytes from blood to lymph. Labeled TDL were injected i.v. into rats continuously receiving IFN-gamma via a central venous catheter. The numbers of B, T, CD4+, and CD8+ lymphocytes were determined in blood and thoracic duct lymph for 120 h. IFN-gamma increased the disappearance of TDL from the blood to a similar extent in all subsets. In contrast, the reappearance of B and T lymphocyte subsets in the lymph was decreased: B lymphocytes were affected significantly more than T lymphocytes, whereas CD4+ and CD8+ lymphocytes were affected to a similar extent. Our study suggests that differential retention within the tissue rather than preferential immigration into the tissue creates a microenvironment with a distinct composition of lymphocyte subsets.

An enzyme-linked immunosorbent assay for the quantification of solubilized CD14 in biological fluids

A simple and robust two site-binding ELISA for the quantification of solubilized CD14 in human and animal body fluids is described. The principle of the assay depends on the specific binding of sCD14 to two monoclonal antibodies (MEM-18, RoMo-1) recognizing different epitopes of this glycoprotein. The detection limit for sCD14 was 1 ng/ml. The method was used to quantify sCD14 in different biological fluids, giving an intra-assay coefficient of variation and an interassay coefficient of variation of about 9%. The assay was used to measure sCD14 in human serum and plasma and other body fluids in health and disease, and in cell culture supernatants. With the exception of monkeys there was no reactivity with 29 other species screened. In healthy volunteers the sCD14 serum level had a mean value of 3.98 +/- 0.3 micrograms/ml (mean SEM, n = 102).

Random entry of circulating lymphocyte subsets into peripheral lymph nodes and Peyer's patches: no evidence in vivo of a tissue-specific migration of B and T lymphocytes at the level of high endothelial venules

Lymphocytes continuously migrate through the body and thus immune competent cells are constantly delivered to most tissues. They interact with high endothelial venules (HEV) via specific homing receptors and vascular addressins, and these molecules seem to be the reason for a preferential homing of B lymphocytes into Peyer's patches and of T lymphocytes into peripheral lymph nodes. When lymphocytes derived from lymph node cell suspensions were applied in the in vitro lymphocyte/endothelium binding assay, the well-known preference of mouse lymph node B lymphocytes for Peyer's patch HEV compared to peripheral lymph node HEV was confirmed in the rat (2.8 times). When in the same in vitro assay thoracic duct lymphocytes (TDL) were used this preference was far less obvious (1.4 times). However, by injecting rat TDL intravenously and by tracing them directly in HEV, B, T, CD4+ and CD8+ lymphocytes are seen to enter Peyer's patches and peripheral lymph nodes in vivo without preference. Thus, in contrast to lymphocytes from lymph node cell suspensions, no evidence was found of a tissue-specific migration of thoracic duct B, T, CD4+ and CD8+ lymphocytes at the HEV level. This finding demonstrates the importance of considering both experimental conditions and the cell source used when investigating lymphocyte traffic.

Splenic autotransplantation provides protection against fatal sepsis in young but not in old rats

Splenectomy increases the risk of contracting infections with high mortality. Thus, splenic tissue should be repaired orthotopically whenever possible. If all attempts fail, splenic autotransplantation might be a suitable method for splenic salvage. The protective function of such transplants in adults has been questioned, leading to a decreased frequency of splenic autotransplantations. However, the regeneration of splenic tissue is better in the young organism than in the old, suggesting that the protection provided by regenerated splenic tissue might be more reliable in children than in adults. In addition, children are at a higher risk in the case of overwhelming postsplenectomy sepsis. The protection warranted by regenerated splenic tissue after autotransplantation at different ages was examined using a highly standardized animal model. Sham operation, splenectomy, and splenic autotransplantation were performed on adult, weanling, and newborn rats, and Streptococcus pneumoniae was applied intranasally 9 months after the operation. After pneumococcal challenge about 80% of the splenectomized animals in the different age groups died of infection, whereas only 20% of the sham operated rats died. Regenerated splenic tissue resulting from splenic autotransplantation performed on adult or weanling rats demonstrated no protective function. However, in newborn rats with transplanted splenic tissue, both survival rate and survival time were increased significantly. Determination of lymphocyte subsets in the blood did not allow the protective role of splenic transplants to be predicted. This study indicates that disappointing results of splenic autotransplantation in adult patients should not lead to false pessimism about the role of this operation in children.

Hemodynamic effects of continuous spinal anesthesia: a comparative study between low and high doses of bupivacaine

BACKGROUND AND OBJECTIVE

Arterial hypotension is a major side effect of spinal anesthesia. Continuous spinal anesthesia may allow titration of the amount of local anesthetic to obtain a level that is appropriate for the surgical procedure.

METHODS

This study compared the hemodynamic effects and the quality of analgesia of spinal anesthesia performed with 3 ml of either 0.125% (n = 12) or 0.5% (n = 13) plain bupivacaine in 25 elderly patients undergoing orthopedic surgery.

RESULTS

The initial dose's duration of action (time elapsed between the end of injection and the first patient's complaint of pain during surgery) was shorter in the group receiving 3 ml of 0.125% plain bupivacaine than in the group receiving 0.5% plain bupivacaine: 80 +/- 31 minutes versus 114 +/- 37 minutes, respectively (mean +/- SD; p less than 0.05). In 6 (50%) of 12 patients of the 0.125% group and in 2 (15%) of 13 of the 0.5% group, analgesia became insufficient during the surgical procedure, necessitating injection of an additional 1 ml (top-up) of the previous solution. All subjects obtained good anesthesia for the entire procedure. The mean dose of bupivacaine necessary for the procedure was significantly lower in the 0.125% group (4.8 +/- 1.3 mg) compared with the 0.5% group (16.1 +/- 3 mg). For a similar maximal upper level of analgesia (T4-T12 in the 0.125% group versus T2-T10 in the 0.5% group), the decrease in systolic arterial pressure was more pronounced in the 0.5% group than in the 0.125% group during the period 15-40 minutes after induction of spinal anesthesia (p less than 0.05%). The mean dose of ephedrine was threefold larger in the 0.5% group than in the 0.125% group.

CONCLUSION

Continuous spinal anesthesia with small amounts of 0.125% plain bupivacaine produces effective anesthesia for orthopedic procedures in elderly patients with minimal hemodynamic changes.

Distribution of lymphocyte subsets and natural killer cells in the human body

The frequency and distribution of B and T lymphocyte subsets have been determined in many body tissues and fluids by preparing cell suspensions and tissue sections from lymphoid and nonlymphoid organs. In humans these studies often concentrate on the blood or on one particular cell source for obvious reasons. However, such data can only be interpreted correctly if the whole immune system is taken into consideration [64]. To facilitate this, reports on the frequencies and the absolute numbers of B and T lymphocyte subsets within various human tissues and fluids have been collected from a wide variety of journals and are briefly summarized here. Since the size of lymphoid organs varies with age (e.g. thymus, tonsils), only the data of adult individuals were included, unless otherwise stated. Natural killer (NK) cells are morphologically quite similar to lymphocytes [59], but very different functionally. For example, they are not able to recirculate from the blood via the lymph nodes and the thoracic duct back to the blood as lymphocytes do [19]. Thus, human NK cells have been compared with lymphocytes with respect to number and distribution.

The role of the spleen in lymphocyte migration

In all species studied so far it was found that more lymphocytes migrate to the spleen than to all the lymph nodes together. Specific molecules on lymphocytes and endothelial cells regulate their entry into lymph nodes, but none of the known molecules play a role in homing to the spleen. The splenic compartments, comprising the red pulp, marginal zone, periarterial lymphatic sheath (PALS) and follicles, all show different kinetics for migrating lymphocytes. By combining 51Cr lymphocyte labeling with morphometry and two color immunohistochemistry, the migratory route of lymphocyte subsets can be followed through the spleen and absolute numbers of lymphocytes calculated in each compartment. T lymphocytes home preferentially to the PALS and B lymphocytes home not only to follicles but also in large numbers to the marginal zone and red pulp. CD4+ and CD8+ lymphocytes migrate similarly at early time points, but at 24 hours CD4+ lymphocytes are preferentially found in the PALS with CD8+ lymphocytes in the red pulp and marginal zone. The functional significance of the different routes of lymphocytes through the spleen has yet to be defined in relationship to specific immune functions and regulatory factors on splenic lymphocyte homing.

Lymphocyte subsets in the blood: a diagnostic window on the lymphoid system?

The assessment of peripheral blood lymphocyte numbers and ratios has been performed in almost every conceivable disease state, but do these values give any useful information about immune status? Jürgen Westermann and Reinhard Pabst try to answer this question and to put peripheral blood population assessments into the whole-body context.

The in vitro lymphocyte/endothelium binding assay. An improved method employing light microscopy

The in vitro lymphocyte binding assay (HEV assay) has proved to be a useful approach for examining the first step of lymphocyte migration, i.e., homing to organs containing high endothelial venules (HEVs). Since fluorescence-labelled standard lymphocytes are usually included in each assay to account for day-to-day variations, HEV preparations have to be evaluated by fluorescence microscopy. Thus no counterstaining can be performed and HEVs without adherent lymphocytes cannot easily be recognized. Because the preparations are not suitable for storage they must be evaluated within a short time. In this study an improved technique is described which permits HEV preparations made with fluorescence-labelled standard lymphocytes to be evaluated by light microscopy in counterstained sections. The phenotypes of the sample lymphocytes can be determined by staining for surface antigens on the same slides and the preparations obtained are permanent.

Modulation of Forssman glycosphingolipid expression by murine macrophages: coinduction with class II MHC antigen by the lymphokines IL4 and IL6

In contrast to murine spleen M phi, resident peritoneal M phi from health mice express very little Forssman glycolipid antigen (Fo). The following experiments suggest that Fo expression by peritoneal M phi may be associated with inflammation. Balb/c and CBA/J mice were given inflammatory stimuli by i.p. injection of live BCG, thioglycollate (TG), Corynebacterium parvum (CP), proteose peptone (PP), or LPS. Control animals received pyrogen-free saline. Expression of Fo and Ia antigen by peritoneal M phi was determined by immunofluorescence after 4 d. Application of TG or CP led to an up to 30-fold increase in Fo+, Ia+ double positive M phi over that in control animals. LPS caused mainly an increase in the percentage of double-positive M phi, whereas no effects were seen in BCG or PP treated animals. To clarify the possible involvement of cytokines in this process and to identify these, the effects of LPS and various cytokines on in vitro induction of Fo and Ia expression were studied in further experiments. LPS, IL6, and IL4 caused induction of up to 15% Fo+ and Ia+ M phi after a 4 d culture period. M phi colony stimulating factor (M-CSF) from lung-conditioned medium was also moderately active. IL1, TNF, and IL2 had no influence, whereas IFN-gamma only induced Ia. For a successful in vitro induction of Fo and Ia, a prior priming of the mice with PP appeared mandatory. This suggests that only M phi of a certain developmental stage can acquire Fo under the influence of the appropriate cytokines. The data may provide the first evidence for cytokine-mediated modulation of a glycolipid antigen of known chemical structure.

Absolute numbers of lymphocytes subsets migrating through the compartments of the normal and transplanted rat spleen

Lymphocyte migration is one of the basic principles of the immune system. Up to now lymphocyte migration experiments have been performed either in a quantitative way, determining whole organ recoveries of radiolabeled lymphocytes without histologic localization, or based on autoradiography which does not provide absolute numbers of immigrant lymphocytes. In this study the traffic of lymphocyte subsets through the splenic compartments: red pulp (RP), marginal zone (MZ), periarteriolar lymphatic sheath (PALS) and follicle was evaluated in absolute numbers. In normal spleens and splenic transplants fluorescein isothiocyanate (FITC)-labeled immigrant lymphocytes were localized and characterized immunohistochemically in cryostat sections by light microscopy. In addition morphometry of the splenic compartments was performed and the recovery of 51Cr-labeled lymphocytes in the spleen was determined. The combination of these methods allowed total numbers of immigrant subset cells to be calculated in individual splenic compartments. At 15 min about 17% of the injected B lymphocytes were found in the MZ. This is the largest fraction of an injected lymphocyte subset found in a single splenic compartment. At 24 h immigrant B cells were not only found in the follicle, but they had reached comparable numbers in the three compartments: follicle, RP and MZ. Most immigrant T lymphocytes were found in the PALS, which from 6 h after injection onwards contained more T cell immigrants than any single organ of the body. CD4+ and CD8+ lymphocytes showed a similar distribution throughout the splenic compartments at early time points. At 24 h CD4+ lymphocytes homed preferentially to the PALS, whereas CD8+ cells seemed to prefer the RP and MZ. Both CD4+ and CD8+ cells also migrated into the follicles. In regenerated splenic tissue after autotransplantation lymphocyte immigration was reduced in all compartments and to the MZ in particular. An impaired lymphocyte migration to the MZ in splenic transplants may be one reason for the lack of protection provided against bacterial infections. Thus examining lymphocyte migration in absolute numbers provides additional information which cannot be gained by determining labeling indices or percentages of lymphocyte subsets alone.

Lymphocyte subsets in the blood. The influence of splenectomy, splenic autotransplantation, ageing, and the site of blood sampling on the number of B, T, CD4+, and CD8+ lymphocytes in the rat

Removal of the largest single lymphoid organ, the spleen, leads to an increase in severe infections. To prevent this, transplantation of splenic fragments can be performed, which may, however, cause an increase in CD8+ lymphocytes in the blood of these patients. This is controversial since in the clinical situation it is often difficult to account for the different age of the patients, the time point after the operation and many other factors known to influence the number of lymphocyte subsets. Using a well-defined animal model, B, T, CD4+, and CD8+ lymphocytes were determined preoperatively in adult rats. Then, either sham splenectomy, splenectomy, or splenic autotransplantation was performed and the animals were followed up for 15 months after the operation. The surgical procedure itself, the site of blood sampling and ageing all influenced the number of lymphocyte subsets profoundly. Furthermore, giving the data as relative or absolute numbers leads to different results. Splenectomy caused lymphocytosis, due to a significant increase in B and CD8+ lymphocytes, as did splenic autotransplantation, which indicates that the number of lymphocyte subsets in the blood should not be used to argue in favour of or against splenic autotransplantation. This study demonstrates that the number of lymphocyte subsets in the blood is influenced by many factors and therefore should be determined in a highly standardized fashion.

Proliferation of macrophage subpopulations in the adult rat: comparison of various lymphoid organs

Adult male Lewis rats received a single intravenous injection of 5-bromo-2'-deoxyuridine (BRDU) to label all proliferating cells in the S-phase of the cell cycle. Various lymphoid organs were removed 1 and 24 hr after injection to assess local proliferation and migration of newly formed cells, respectively. In cell suspensions, surface staining was performed for macrophage subsets (ED1, ED2, ED3), and the DNA label BRDU was detected by a monoclonal antibody. Local proliferation of ED1+ macrophages occurred in all organs investigated with the exception of the blood. Bone marrow outweighed the other organs by far; in addition to the proliferating ED1+ promonocytes, the bone marrow also contained BRDU-labeled ED2+ macrophages. Newly formed ED1+ monocytes migrated into lymphoid organs such as the mesenteric lymph nodes and spleen where they comprised about 90% of newly formed macrophages. In the spleen, ED3+ macrophages seemed to be renewed by local proliferation, whereas in the mesenteric lymph nodes these cells were replaced by immigration. The heterogeneity of macrophages was further demonstrated by the different renewal of splenic macrophages. ED1+ and ED3+ cells were replaced in a matter of days, whereas it would probably take several months to renew ED2+ cells.

Immunohistological localization and characterization of FITC-labelled lymphocytes. A rapid and inexpensive method for studying migration

Immunohistochemical methods are described for the detection and characterization of fluorescein isothiocyanate (FITC)-labelled lymphocytes on cryostat sections using an anti-FITC antibody. As a model, the localization of thoracic duct lymphocytes (TDL) in the rat spleen was examined at three time intervals. The kinetic patterns observed clearly differed between the four splenic compartments examined, namely: the red pulp, the marginal zone, the periarteriolar lymphatic sheath (PALS) and the follicle. Furthermore, the subset composition of the immigrant lymphocytes was determined by two colour immunohistochemical staining, which permitted simultaneous detection of the FITC label and surface markers. The results suggest that this method is a fast, easy and inexpensive approach to studies of lymphocyte migration.

Proliferation of lymphocyte subsets in the adult rat: a comparison of different lymphoid organs

Adult, male Lewis rats received a single injection of 5-bromo-2'-deoxyuridine (BrdUrd) i.v. to label proliferating cells in the S phase of the cell cycle. After 1 and 24 h the thymus, bone marrow, blood, spleen, peripheral, cervical and mesenteric lymph nodes as well as Peyer's patches were removed. In cell suspensions surface staining was performed for B, T, T helper (Th) and cytotoxic/suppressor (Tc/s) T lymphocytes by identifying kappa light chain, CD5+, CD4+ and CD8+ cells, respectively. On the same slide the DNA label BrdUrd was demonstrated by a monoclonal antibody. B, T, Th and Tc/s lymphocytes proliferate locally both in central lymphoid organs such as the thymus and the bone marrow, and in peripheral lymphoid organs such as the spleen, lymph nodes and Peyer's patches. Within an organ the amount of proliferation among the lymphocyte subsets is similar, differing not more than threefold. Although concerning only a small fraction of cells within the organ, an unexpected finding is the high percentage of BrdUrd-labeled cells among B lymphocytes in the thymus (3%) and among T lymphocytes in the bone marrow (3%). One day after injection of BrdUrd the thymus contains 25% BrdUrd+ T lymphocytes, while the other organs investigated do not show more than about 2% BrdUrd+ B and T lymphocytes. Many of the newly formed lymphocyte subsets leave their organ of birth within 24 h. Thus the amount of proliferation in the lymphocyte subsets investigated is very similar and the differences between central (thymus and bone marrow) and peripheral lymphoid organs are much smaller than expected.

The mucosa of the male genital tract; part of the common mucosal secretory immune system?

The selective migration of mucosal-derived lymphoid blasts to other mucosal organs is taken to be an essential part of the common secretory immune system. In rats, proliferating lymphoid cells from mesenteric lymph nodes (mLN) and peripheral lymph nodes (pLN) were labeled in vitro using two different techniques, in order to test the hypothesis that the mucosa of the male genital tract is a preferential site for mLN lymphoid blasts to home to. A low but significant migration to male genital organs was found, but with no difference between blasts from pLN and mLN. Thus there is no evidence to include the male genital tract in the common mucosal secretory immune system. Recirculating lymphocytes from the thoracic duct entered the male genital organs with a similar distribution to the pattern of lymphoid blasts. There is probably an exchange between these immigrating lymphocytes and the different subsets, which are localized in the epithelium (T suppressor) and interstitial tissue (T helper) in male genital organs. The lymphoid cells in the male genital tract might play an important role in the immune function of seminal fluid and in sexually transmissible diseases.