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.

Migration pattern of lymphocyte subsets in the normal rat and the influence of splenic tissue

Lymphocyte subsets leave the blood and appear in the thoracic duct of normal rats at different rates. The aim of the present study was to investigate their migration pattern through blood, spleen, bone marrow, mesenteric lymph nodes, and Peyer's patches in normal Lewis rats and to study the role of the spleen using splenectomized and spleen-transplanted animals. Fluorescein isothiocyanate (FITC)-labelled thoracic duct lymphocytes (TDL) were injected intravenously into rats and after 15 min, 1, 6, and 24 h the percentages of B, T, T helper (TH) and T-cytotoxic/suppressor (TC/S) lymphocytes in the FITC+ cells were determined in cell suspensions by means of monoclonal antibodies. B and T lymphocytes are preferentially localized in different organs, e.g. B cells in Peyer's patches and T cells in mesenteric lymph nodes. The migration of TH lymphocytes differed from that of TC/S lymphocytes in all the organs investigated. In the late phase after injection the migration of B and TH lymphocytes was influenced by the spleen, since after splenectomy the number of injected B lymphocytes increased and that of TH lymphocytes decreased in all organs investigated except the bone marrow. Splenic autotransplantation could not normalize the disturbed migration.

Immunoarchitecture of regenerated splenic transplants: influence of donor and host age on the regeneration of splenic compartments

Inbred rats were used as a model to determine the influence of the age of the implanted splenic tissue and the age of the host on the structure of transplanted splenic tissue. Monoclonal antibodies against lymphocyte, macrophage and dendritic cell subsets were used to evaluate the different compartments of the spleen. Adult rats received implants from adult, weanling or fetal rats, weanling rats received splenic tissue from adult, weanling or fetal rats and neonatal rats received neonatal or fetal spleens. There were major differences in the structure and cellular composition of the regenerated splenic tissue. The younger the recipients and the donor spleens, the better the normalization of the splenic compartments and the less fibrous tissue was found 3 months after transplantation. The follicles regenerated in all transplants, but the marginal zone was only normally developed in wealing and neonatal hosts. The periarteriolar lymphatic sheath regenerated in a similar manner to the marginal zone. Whenever a compartment developed, its cellular composition was the same as in a normal spleen. The immunohistological techniques enabled splenic regeneration to be characterized revealing a far from normal histological splenic structure in many age groups. These findings suggest that splenic regeneration in children might result in splenic tissue with normal compartments, which would be in contrast to some data in adults.

Influence of donor and host age on the regeneration and blood flow of splenic transplants

After splenectomy there is an increased risk of fatal overwhelming postsplenectomy sepsis, especially in children. If all alternatives to splenectomy fail, autotransplantation of splenic fragments is indicated. These fragments regenerate after a necrotic phase to small splenic nodules. Regulatory factors governing the regeneration process are largely unknown. Inbred rats were used as a model to define the influence of recipient and donor age on the regenerated mass and the blood flow of transplanted splenic fragments. These are both important factors for the protective function of the spleen. Fetal, newborn, weanling, or adult spleens were implanted into the greater omentum of newborn, weanling, or adult rats. The younger the recipient and donor, the better the regeneration and perfusion of transplants. However, these did not reach more than 40% of the normal splenic mass. In addition, no experimental group achieved more than one third of the normal splenic blood flow. There is an obvious age dependency in splenic regeneration and blood flow, but the transplants are far from attaining a normal splenic mass and perfusion.

Blood transit and recirculation kinetics of lymphocyte subsets in normal rats

Thoracic duct lymphocytes (TDL) were labelled with fluorescein isothiocyanate (FITC) and injected into normal, unanaesthetized rats with either a central venous catheter or a thoracic duct cannula. The blood transit time and the appearance in the lymph was calculated and then the percentages of B, T, T helper, and T suppressor lymphocytes were determined with monoclonal antibodies (Ox12, Ox19, W3/25, and Ox8, respectively). The blood transit time of all subsets was about 30 min. However, the percentage of B lymphocytes from 5 min after injection onwards is reduced (14.5 +/- 1.9%) compared to the injected TDL (32.7 +/- 1.7%). These cells are not in the lung vascular pool. The recovery of FITC-labelled TDL in the thoracic duct within 48 h is much higher (56.8 +/- 5.3% of the injected lymphocytes) than in previous studies using radioactive markers. B lymphocytes appear later and in a reduced number in the thoracic duct. The mean transit time is 26 h and the recovery 31.5 +/- 4.2% in contrast to T lymphocytes (18 h and 66.3 +/- 6.5%, respectively). The technique of combining FITC in vitro labelling with surface staining after completion of migration does not interfere with lymphocyte migration. It can therefore be used to study the migration of lymphocyte subsets in normal, untreated animals.

Malaria infection in rats with stimulated splenic red pulp: the blood flow and protective effect in normal and transplanted splenic tissue

After splenic autotransplantation both weight and blood flow of the regenerated splenic tissue are decreased. In addition, the protective function of the transplant is less compared to that of the normal spleen. In the present study, the red pulp of normal and transplanted splenic tissue was stimulated by injections of phenylhydrazine to increase the weight, the blood flow, and the protective function. After stimulation, the weight of the normal spleen increased to 900 +/- 70 mg (control 530 +/- 20 mg) and the transplanted tissue to 240 +/- 70 mg (control 70 +/- 20 mg). This enlargement was caused by an increase in the splenic red pulp. However, the relative blood flow decreased in both the normal spleen and the transplant to 50% of the normal value. To evaluate the protective function of the stimulated splenic tissue, normal, splenectomized and transplanted rats were infected with Plasmodium berghei. Despite the dramatic increase in the red pulp, neither the normal nor the transplanted animals showed a survival rate superior to that of the splenectomized animals. The mass of splenic tissue obviously does not correlate with the protective effect of the spleen in parasitic infections.

Integration of clinical problems in teaching gross anatomy: living anatomy, X-ray anatomy, patient presentations, and films depicting clinical problems

In addition to lectures and the dissection course, four supplements are described to stimulate first-year medical students to learn gross anatomy. All topics are coordinated with the dissection course. The additional options are living anatomy, X-ray anatomy by a roentgenologist, presentation of patients by clinicians, and films on clinical problems. This integrated curriculum of basic and applied anatomy generates a high level of student interest in gross anatomy.

Autotransplantation of splenic fragments: lymphocyte subsets in blood, lymph nodes and splenic tissue

Abnormal ratios of T helper-type to T suppressor-type lymphocytes in the blood of patients with replanted autologous splenic tissue led to the present study in rats. Lymphocyte subsets were studied in the blood, mesenteric lymph nodes and spleen after autotransplantation and compared to splenectomized and control rats. In the blood of transplanted rats the percentage of T and T helper-type lymphocytes was lower, in the spleen B lymphocytes higher and T lymphocytes and their subsets lower. Comparable changes were seen in the lymph nodes. The data of the mesenteric lymph nodes in autotransplanted rats did not differ from splenectomized animals. Even after 37 weeks the regenerated splenic tissue only reached 13% of the weight of control rats and the absolute lymphocyte number was only 2.5% of a normal spleen. Splenic autotransplantation results in a small hypocellular mass of splenic tissue with a different composition of lymphocyte subsets and does not correct the obvious effect of splenectomy on lymphocyte subpopulations in lymph nodes.

In situ labelling of bone marrow lymphocytes with fluorescein isothiocyanate for lymphocyte migration studies in pigs

In normal young pigs, the femoral artery and vein were cannulated and after occluding other vessels to one hind leg they were connected to an extracorporeal perfusion system. Fluorescein isothiocyanate (FITC) was added to the perfusate to selectively label cells in the bone marrow. Large numbers (approximately 0.9 X 10(9] of labelled lymphocytes left the bone marrow of one leg within 1 d and migrated via the blood to the bone marrow in other bones, lymph nodes, spleen, Peyer's patches and even into the thymus. On average 1.7% of the lymphocytes in the blood and about 1% within the spleen were labelled. Peyer's patches and the thymus showed very low indices. Thus the bone marrow is an integral part of the migratory route of lymphocytes. Selective labelling of bone marrow cells in their normal microenvironment with FITC is a suitable method for studies of cell migration from the bone marrow.