Theory and practice of immunoregulation by tissue treatment prior to transplantation

Combinatorial Strategies With PD-1/PD-L1 Immune Checkpoint Blockade for Breast Cancer Therapy: Mechanisms and Clinical Outcomes

As an emerging antitumor strategy, immune checkpoint therapy is one of the most promising anticancer therapies due to its long response duration. Antibodies against the programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) axis have been extensively applied to various cancers and have demonstrated unprecedented efficacy. Nevertheless, a poor response to monotherapy with anti-PD-1/PD-L1 has been observed in metastatic breast cancer. Combination therapy with other standard treatments is expected to overcome this limitation of PD-1/PD-L1 blockade in the treatment of breast cancer. In the present review, we first illustrate the biological functions of PD-1/PD-L1 and their role in maintaining immune homeostasis as well as protecting against immune-mediated tissue damage in a variety of microenvironments. Several combination therapy strategies for the combination of PD-1/PD-L1 blockade with standard treatment modalities have been proposed to solve the limitations of anti-PD-1/PD-L1 treatment, including chemotherapy, radiotherapy, targeted therapy, antiangiogenic therapy, and other immunotherapies. The corresponding clinical trials provide valuable estimates of treatment effects. Notably, several combination options significantly improve the response and efficacy of PD-1/PD-L1 blockade. This review provides a PD-1/PD-L1 clinical trial landscape survey in breast cancer to guide the development of more effective and less toxic combination therapies.

Influence of the nature of coupling agents on insulin adsorption on supports grafted with sialic acid for high-performance affinity chromatography

Porous silica exhibits excellent mechanical properties for use as a stationary phase for high-performance liquid chromatography. However, negative surface charges make it unusable in its native state. For this reason, silica beads are coated with dextran polymers carrying a calculated amount of diethylaminoethyl groups. Both the minimization of non-specific interactions and the hydrophilic character of such supports allow their functionalization with biospecific ligands and finally their use in high-performance affinity chromatography of biological products. The use of these modified supports in high-performance affinity chromatography requires a better understanding of various characteristics of stationary phases. For this purpose, several techniques were utilized, in particular, size-exclusion chromatography and adsorption of radiolabelled albumin. These methods provided complementary information on the structure of these supports. Coated silica-based supports were functionalized with sialic acid by means of different coupling agents. The affinity of these supports for insulin was determined by the establishment of adsorption isotherms and by high-performance affinity chromatography, to evidence the relationships between structural characteristics of the supports and their separation properties. The study of interactions between these supports and insulin allowed us to show the importance of the coupling method on the performances of supports in affinity chromatography.

Rejection of spontaneously accepted rat liver allografts with recipientinterleukin-2 treatment or donor irradiation

While MHC incompatible DA (RTl(a)) to Lewis (RT1(1), LEW) rat liver allografts are acutely rejected, the reciprocal LEW to DA liver grafts are spontaneously accepted. The mechanism of this acceptance remains unclear. We evaluated the effect of donor treatment with total body irradiation (TBI) or gadolinium chloride (GdCl3), and recipient treatment with exogenous IL-2 after transplantation on the survival of the spontaneously accepted liver grafts. Male LEW and DA rats were used as donors and recipients for orthotopic liver allo- or iso-graft transplants. The LEW liver donor was treated by TBI (10 gray) 7 days before transplantation, or LEW donor Kupffer cell phagocytosis was blocked with GdCl3 (7 mg/kg) on days -2 and -1 pretransplant. In an attempt to reverse LEW liver graft acceptance, 180,000 units human IL-2 (hIL-2) were administered daily IP to the DA liver recipients from days 1 to 7 after liver grafting. While untreated LEW recipients rejected DA liver grafts within 13 days, DA recipients accepted LEW livers indefinitely (>302 days). In contrast, irradiation of the LEW liver donor prevented the spontaneous acceptance by DA recipients, and resulted in acute rejection of the liver grafts in 9-20 days. However, spontaneous graft tolerance was restored by parking the irradiated LEW donor liver in naive LEW rats for 48 hr before retransplantation to DA recipients (>50 days). When LEW donors were treated with GdCl3, which is known to block Kupffer cell phagocytosis and antigen processing, the spontaneous acceptance of the LEW liver grafts by DA recipients was unaffected. However, when exogenous rhIL-2 was given daily, LEW liver allografts were rejected by the DA recipients. The resulting liver failure correlated with a progressive increase in serum bilirubin and the development of a predominantly lymphocytic portal tract infiltration, bile duct epithelial damage, and portal vein endothelitis, which is consistent with acute allograft rejection. LEW and DA recipients of liver isografts developed no toxicity and survived indefinitely (>100 days) when treated with the same dose of IL-2. These results indicate that spontaneous rat liver allograft acceptance is associated with the presence of radiosensitive cells in the donor liver that may interact with recipient T cells to inhibit (Th1) production of IL-2.

The immunology of the human foetal pancreas aged 8-13 gestational weeks

The expression of MHC class I and class II antigens by the human foetal pancreas (HFP) during the first trimester is poorly documented. Using immunohistochemical techniques, we analysed 37 HFPs aged 8-13 gestational weeks (gw) and compared the results with those of 9 HFPs aged 14-16 gw. In all of the specimens, the ductal cells were class I- and class II-negative. Islets and endothelial cells expressed class I but were class II-. Interstitial class II+ cells included macrophages, B lymphocytes and dendritic-like cells that were negative for macrophage markers. While the frequency of class II+ cells in the HFP remained constant from 8 to 13 gw, a threefold increase was observed from the end of the 13th gw to the 16th gw. In conclusion, the lower density of interstitial class II+ cells in HFPs aged 8-13 gw indicates that immunomodulation is likely to be more successful in this age group.

Function of lymphocytes and macrophages after cryopreservation by procedures for pancreatic islets: potential for reducing tissue immunogenicity

The survival of tissue allografts can be extended by pretreating the tissue to remove the stimulatory leucocytes that populate the graft; with this in mind, we have recently begun to explore a cryobiological approach to modulating tissue immunogenicity by using the differential susceptibility of different cells to freezing injury. The sensitivity of leucocytes to fast cooling rates, which were used in procedures that have been reported to yield viable pancreatic islets of Langerhans, was examined. The loss of both cell numbers and the ability of peripheral blood lymphocytes to undergo blastogenic transformation in response to the mitogen concanavalin A after freezing and thawing was determined over a range of cell concentrations using the "curve-shift" method. Lymphocytes frozen at 1 degree C/min by a control procedure that was designed to yield maximum survival of lymphocytes showed that although there was a decrease in the number of responding cells, there was no reduction in the ability of the recovered cells to undergo blastogenesis when compared with the response of nonfrozen cells. However, cooling at 1 degree C/min in the experimental procedures resulted in both the loss of cells as well as a marked reduction in the ability of recovered cells to incorporate 125I-deoxyuridine into nucleic acid. Cells cooled at either 20 or 75 degrees C/min by any of the procedures showed total inability to respond to stimulation. Lysozyme is produced continuously by all types of macrophages in culture. The large net increase in total lysozyme content of macrophage cultures is therefore a useful measure of the viability of these accessory cells. Cooling at 1 degree C/min by a control, optimized procedure yielded 91% survival of viable peritoneal exudate cells. Cooling at either 1 or 20 degrees C/min in the experimental procedures resulted in 72-75% survival of cells frozen by one method and 33% survival when frozen by an alternative procedure. Negligible recovery of viable cells was obtained after cooling at 75 degree C/min. The preservation protocols employed in this study differ significantly in the variables known to influence the survival of the cells; these include the concentration of cryoprotectant (CPA), the length and temperature of exposure to CPA, the dilution regimen, and the optimum cooling rate for survival of pancreatic islets. This study therefore defines clearly those conditions most likely to effect a depletion of "passenger" lymphoid cells by freezing during the cryopreservation of islets of Langerhans.

Continuous flow electrophoretic separation of proteins and cells from mammalian tissues

A new continuous flow electrophoretic separator for cells and macromolecules was built and tested in laboratory experiments and in the microgravity environment of space flight. Buffer flows upward in a 120-cm long flow chamber, which is 6 cm wide X 1.5 mm thick in the laboratory version and 16 cm wide X 3.0 mm thick in the microgravity version. Electrophoretic subpopulations are collected in 197 fractions spanning 16 cm at the upper end of the chamber. The electrode buffer is recirculated through front and back cooling chambers, which are also electrode chambers. Ovalbumin and rat serum albumin were used as test proteins in resolution and throughout tests; resolution of these two proteins at 25% total w/v concentration in microgravity was the same as that found at 0.2% w/v concentration in the laboratory. Band spreading caused by Poiseuille flow and conductance gaps was evaluated using polystyrene microspheres in microgravity, and these phenomena were quantitatively the same in microgravity as in the laboratory. Rat anterior pituitary cells were separated into subpopulations enriched with cells that secrete specific hormones; growth-hormone-secreting cells were found to have high electrophoretic mobility, whereas prolactin-secreting cells were found to have low electrophoretic mobility. Cultured human embryonic kidney cells were separated into several electrophoretic subfractions that produced different plasminogen activators; a medium-high-mobility subpopulation and a medium-low-mobility subpopulation each produced a different molecular form of urokinase, whereas a high- and an intermediate-mobility subpopulation produced tissue plasminogen activator. Canine pancreatic islets of Langerhans cells were separated into subpopulations, which, after reaggregation into pseudoislets, were found to be enriched with cells that secrete specific hormones; insulin-secreting beta cells were found in lowest mobility fractions, whereas glucagon-secreting alpha cells were found in the highest mobility fractions. Results of particle electrophoresis experiments were comparable in microgravity and in the laboratory, since cell densities that overloaded the carrier buffer (resulting in zone sedimentation) were avoided, and a 500-fold increase in protein throughput was achieved without compromising resolution in microgravity.

The effect of immunosuppressive agents on lymphocyte subsets in rat peripheral blood

A method for monitoring circulating lymphocytes subsets in the rat on an automated flow cytometer with monoclonal antibodies was used to ascertain in vivo effects of various doses of immunosuppressive agents. The agents tested were anti-lymphocyte serum (ALS), azathioprine (AZA), cyclophosphamide (CTX), cyclosporin A (CsA) and methylprednisolone (MP). Each immunosuppressive agent varied in its capacity to induce changes in T cell subsets and B cell numbers. The rapidity of onset of action of the agents varied considerably; with ALS and MP maximal effects were seen within hours whilst the effects with CsA, cyclophosphamide (CTX) and azathioprine (AZA) took several days to develop. ALS had marked anti-T cell activity but did not selectively affect the T cell subsets. AZA and CTX both exerted their major effect upon the B cell (OX4+) subpopulation. CsA administration was associated with the appearance of many circulating lymphocytes which expressed the pan-T marker (W3/13) but neither of the T cell subset markers (W3/25, OX8). With CsA there was no significant alteration in the W3/25:OX8 ratio, although a persistent decrease in the number of all T lymphocytes was observed after administration of this drug at a dose of 45 mg/kg had ceased. MP was the only drug which had a marked selective effect on a T cell subset. The numbers of circulating Class II major histocompatibility complex (MHC) reactive lymphocytes (W3/25+) were significantly more depressed than the Class I MHC reactive subset (OX8+). This effect persisted for up to 31 days after the single injection of a depot preparation of this drug, and was found to be associated with prolonged survival of precultured endocrine xenografts.

Pancreatic islet transplantation. Induction of graft acceptance by ultraviolet irradiation of donor tissue

The effect of ultraviolet (UV) irradiation on the immunogenicity of rat pancreatic islets was examined in allograft and xenograft models. Direct UV irradiation (900 J/m2) of Lewis islets, isolated and hand-picked, does not alter pancreatic islet endocrine function in isograft experiments and results in indefinite islet allograft survival in streptozocin diabetic ACI rats without chronic immunosuppression. Direct UV irradiation, at an appropriate dose, also leads to indefinite islet xenograft survival of Lewis islets in B10-BR diabetic mice and prolonged survival of rat islets in Balb/C mice. When direct UV irradiation of islet allografts did not result in indefinite islet allograft prolongation [Wistar/Furth (W/F) to diabetic Lewis], the addition of brief peritransplant immunosuppression with cyclosporine (days 0, +1, and +2) resulted in permanent acceptance of islet allografts, a result not achieved by cyclosporine alone. The effectiveness of UV irradiation in abrogating islet allograft rejection in several experimental models is supported by in vitro studies showing that UV irradiation of stimulator cells, peripheral blood lymphocytes, splenocytes, and isolated rat dendritic cells abolishes any significant stimulation by such cells of totally histoincompatible thoracic duct responder lymphocytes. In vitro nonreactivity of mixed lymphocyte culture (MLC) with UV-irradiated stimulator cells and in vivo permanent allograft acceptance are reversed by the addition of a small number of untreated donor-type dendritic cells to either the MLC or the recipient bearing the permanent graft. The authors suggest that the primary effect of UV irradiation on immune alteration of islet allografts and xenografts is due to induction of a major metabolic change in the dendritic cells in the graft. This then leads to defective antigen presentation and results in either permanent or prolonged allograft and xenograft acceptance, depending on the degree of MLC stimulation between the islet donor and the diabetic recipient.