Impact Of Immunosuppressive Drugs Research Articles

Autoimmunity and Cancer: Two Stations on the Same Continuum.

Autoimmunity has been associated with different types of cancer, including hematological malignancies like lymphomas, and solid tumors. Additionally, the potential role of medication-induced immunosuppression should be considered. Our study aimed to investigate the relationship between autoimmunity and the development of cancer, as well as the impact of immunosuppressive drugs on increasing cancer risk. The study sample was composed of patients who developed cancer after the administration of biological agents for the treatment of autoimmune disorders. Selected patients were treated in our hospital between 1st January 2011 and 31st December 2021 and followed up in internal medicine, gastroenterology, or dermatology consult. From 434 patients with autoimmune diseases using biological agents, only 20 developed cancer, which was our final study sample. The data analysis was performed using the IQVIR package version 2.0.2 (IQVIA, Durham, NC). A p-value of <0.05 was considered statistically significant. We found a significant correlation between long-term corticosteroid therapy and an increased risk of cancer. However, the effect of biological therapies on cancer risk was not statistically significant. It's worth noting that our sample size was small, so we cannot extrapolate these findings. Physicians need to be aware that treating autoimmune diseases with immunosuppressive therapies may contribute to the development of cancer. Further research is needed to determine the impact of such treatments on cancer prognosis.

The Effects of Immunosuppressive Drugs on the Characteristics and Functional Properties of Bone Marrow-Derived Stem Cells Isolated from Patients with Diabetes Mellitus and Peripheral Arterial Disease.

Diabetic patients (DPs) with foot ulcers can receive autologous cell therapy (ACT) as a last therapeutic option. Even DPs who have undergone organ transplantation and are using immunosuppressive (IS) drugs can be treated by ACT. The aim of our study was to analyze the effects of IS drugs on the characteristics of bone marrow-derived stem cells (BM-MSCs). The cells were isolated from the bone marrow of DPs, cultivated for 14-18 days, and phenotypically characterized using flow cytometry. These precursor cells were cultured in the presence of various IS drugs. The impact of IS drugs on metabolic activity was measured using a WST-1 assay, and the expression of genes for immunoregulatory molecules was detected through RT-PCR. Cell death was analyzed through the use of flow cytometry, and the production of cytokines was determined by ELISA. The mononuclear fraction of cultured cells contained mesenchymal stem cells (CD45-CD73+CD90+CD105+), myeloid angiogenic cells (CD45+CD146-), and endothelial colony-forming cells (CD45-CD146+). IS drugs inhibited metabolic activity, the expression of genes for immunoregulatory molecules, the production of cytokines, and the viability of the cells. The results indicate that IS drugs in a dose-dependent manner had a negative impact on the properties of BM-MSCs used to treat ischemic diabetic foot ulcers, and that these drugs could affect the therapeutic potential of BM-MSCs.

EpITRANS, impact of immunosuppressive drugs on epithelial immunity in acute respiratory infections of solid organ transplant recipients

EpITRANS, impact of immunosuppressive drugs on epithelial immunity in acute respiratory infections of solid organ transplant recipients

Impact of Immunosuppression on the Severity of SARS-CoV-2 Infection in Renal Transplant Recipients

Abstract: Kidney transplant patients have a high case fatality rate following severe acute respiratory syndrome 2 (SARS-CoV-2) infection. In addition, the vaccine immune response is lower and less durable, which makes them more susceptible to severe forms, even when vaccinated. Evidence suggests that in addition to advanced age and the high prevalence of comorbidities often associated with worse prognosis, such as diabetes, obesity, and cardiovascular disease, prolonged immunosuppression exerts an independent effect on outcomes. In fact, the cellular and humoral adaptive immune response, which is inhibited by immunosuppression, is a key step in resolving SARS-CoV-2 infection. On the other hand, lymphocyte inhibition could modulate the aberrant production of proinflammatory cytokines that result in severe lung impairment, mitigating the severity of the condition. In addition, some immunosuppressive drugs have antiviral properties, potentially applicable to coronavirus. This narrative review aimed to discuss the available evidence on the impact of immunosuppressive drugs on COVID-19 outcomes in kidney transplant recipients

Impact of Immunosuppressive Drugs on Fibroblasts: An In Vitro Study.

Background: The aim of this study was to compare the direct impact of different agents for immunosuppressive therapy on mouse fibroblasts as a possible cause of drug-induced gingival overgrowth (DIGO). Methods: 3T3 mouse fibroblasts were cultivated in cell-specific media (2 × 104 cells/mL) and treated for 6, 24, 48 and 72 h with one of three immunosuppressive drugs (IsDs): cyclosporin a (CsA), tacrolimus (TaC) and sirolimus (SiR). Different concentrations (10–750 ng/mL) were used to mimic serum levels under active immunosuppressive therapy conditions. Cell population characteristics (cell number, viability and morphology) were assessed using computer-assisted cell analysis. Expression of pro-collagen type I carboxy-terminal propeptide (PICP) was identified using an ELISA assay. Results: The influence of IsDs on the biological status of 3T3 fibroblasts was time- and dose-dependent. Comparing CsA and TaC, the total cell amount was enhanced using concentrations in the range of 10–150 ng/mL (p > 0.05). In contrast, treatment with SiR resulted in a decrease in the average cell number (p < 0.01). PICP and cell diameter of fibroblasts were not susceptible to IsD treatment (p > 0.05). Conclusions: Our results revealed time-dependent effects of IsDs, with distinct influences on cell number. The cell morphology and the PICP balance of the investigated fibroblast cell line remained unaffected. Hence, the potential role of IsDs is not a unilateral mechanism of action but rather a multifactorial process.

S715 Outcomes of COVID-19 Infections in Patients With IBD and Other IMIDs From a Large Healthcare System

Introduction: Patients with IBD receiving immunosuppressive (IS) therapy may be at higher risk of infectious complications. The impact of IS drugs on COVID-19 outcomes in patients with IBD and other immune-mediated inflammatory disorders (IMIDs) is unclear. We aimed to determine COVID-19 outcomes in a large population database from a single healthcare system. Methods: Adult patients with IBD and other IMIDs were identified using SNOMED-CT codes from the EMR of the Providence Health System. COVID-19 diagnoses were identified based on SARSCoV-2 positive PCR results. COVID-19 incidence, hospitalization, ICU admission and death were analyzed among IBD, other IMID patients and a control group without IMIDs. Risk factors for severe COVID-19 outcomes were estimated using logistic regression with demographics, comorbidities and IMID drugs including corticosteroids, biologics and JAK inhibitors as independent variables. We considered defined drug exposure as having a drug prescribed or administered at least once within the year prior to the first positive SARS-CoV-2 positive test result. Results: We identified 58,612 adult patients with IBD (32,043 UC and 26,569 CD), 130,799 with other IMIDs, and 6,0±6,081 controls without IMID. Among these, there were 59,647 COVID-19 cases (0.95%) including 427 (0.73%) among IBD patients. Of these 80 (18.7%) were hospitalized, 3 (0.7%) required ventilatory support and 10 died (2.3%). COVID-19 incidence was similar among IBD, other IMID and non-IMID controls. Risk factors for severe COVID-19 outcomes are shown in the Table 1. Among IBD patients, only age (aOR 1.04, p=0.0001) was associated with an increased risk of hospitalization whereas steroid, IMM or advanced therapeutic use was not. Age was also a risk factor for hospitalization among other IMID patients whereas the use of immunotherapeutic drugs appeared to be protective. Conclusion: Patients with IBD and other IMIDs do not appear to be at increased risk of COVID-19 infections or related serious complications. Age is the only variable associated with an increased risk factor for hospitalization among patients with IBD and other immune-mediated conditions. Further studies on this topic are warranted.

The Effects of Long-Term Immunosuppressive Therapies on the Structure of the Rat Prostate

Background: Little is known about the overall impact of immunosuppressive drugs on the prostate. The study aimed to determine the impact of different protocols of immunosuppressive treatment on the structure of the rat ventral prostate. Methods: For 6 months, 48 male Wistar rats received immunosuppressive drugs: cyclosporin A, tacrolimus, mycophenolate mofetil, rapamycin, and prednisone, according to three-drug protocols. Light and transmission electron microscopic studies, and quantitative evaluation of immunohistochemical expression of selected intermediate filaments, CD117+ mast cells, and CD138+ plasma cells were performed in the rat ventral prostate. Results: In all experimental groups, acini focal hyperplasia, changes to the ultrastructure of the glandular epithelium, changes in the expression of cytokeratins and desmin, and numerous mast and plasma cells in the prostate stroma were found. In cyclosporine-A-based groups, atrophy and numerous intracellular vacuoles were observed. In groups where a three-drug treatment was replaced with rapamycin, morphological alterations were less severe compared to those without conversion. Conclusions: In the rat ventral prostate, (1) immunosuppressive protocols affect the morphology and immunohistochemical expression of intermediate filaments, (2) morphological alterations, expression, and localization of selected proteins are not connected with adenocarcinoma development, and (3) conversion of the treatment to rapamycin may prevent hyperplastic abnormalities.

Impact of immunosuppressive drugs in the therapeutic efficacy of autoimmune skin diseases

Background: Autoimmune skin diseases such as pemphigus vulgaris and psoriasis and systemic sclerosis require long-term treatment. Immunosuppressive drug therapy is a gold standard treatment choice in the management of autoimmune skin disease. Aim and Objective: The aim of the study was to assess the efficacy of immunosuppressive drugs in the management of chronic skin diseases. Materials and Methods: A total of 120 cases of both genders (75 males and 45 females), above 18 years and newly started with immunosuppressant drugs for psoriasis (methotrexate therapy-weekly once), Pemphigus Vulgaris and Systemic Sclerosis (pulse therapy – monthly once) were recruited. The clinical response of drugs was assessed by psoriasis area severity index score (PASI), modified Rodnan Skin Score (MRSS), and Pemphigus Area and Activity Score (PAAS). Results: The PAAS score, PASI score, and MRSS scores were significantly decreased from the beginning to the end of the 6th month and the difference was statistically significant (P < 0.005). Nausea/ vomiting were the common adverse effects in all groups followed by gastritis and weight gain. Conclusion: The usage of immunosuppressant drugs such as methotrexate in the management of psoriasis and dexamethasone-cyclophosphamide therapy in the management of pemphigus vulgaris and systemic sclerosis is effective and did not show any major adverse effects.

Impact of Immunosuppressive Drugs on the Metabolism of TCells.

Energetic metabolism supports rapid cell growth and proliferation, differentiation, polarization, and effector functions of T cells. T lymphocytes have the remarkable plasticity that allows them to shape their metabolism to adapt to extracellular and intracellular cues, a process that involves molecular modules referred to as "metabolic checkpoints" that sense metabolic signals and transduce effector messages. These metabolic checkpoints may represent a novel therapeutic strategy for immune modulation. Chemical immunosuppressive drugs including mammalian target of rapamycin inhibitors (sirolimus and everolimus), calcineurin inhibitors (tacrolimus and cyclosporine), and purine and pyrimidine synthesis inhibitors (6-mercaptopurine, mycophenolic acid, and methotrexate) are widely prescribed for the treatment ofautoimmune and inflammatory diseases and for controlling alloimmunity in interfering with the signals that activate and allow T cells to proliferate. Emerging evidence indicates that these drugs also target T-cell metabolism and metabolic checkpoints, which, as a consequence, could contribute to their immunosuppressive effects. These examples raise the issue of how the modulation of these metabolic checkpoints can regulate T-cell activation, differentiation, and function. In this review we highlight emerging concepts about the modulation of metabolic reprogramming in T-cell responses by immunosuppressive drugs and how potential therapeutic interventions influence T-cell fate and effector function.

Impact of immunosuppressive drugs on circulating Tfh cells in kidney transplant recipients: A pilot study

BackgroundT follicular helper cells (Tfh) are recently revealed to be vital in antibody-mediated rejection (AMR) in kidney transplant recipients (KTRs). However, the impact of immunosuppressive drugs on Tfh cells is not fully understood. The purpose of this study was to investigate the variation of Tfh cells phenotypically and functionally in KTRs treated with different immunosuppression regimens. MethodsWe recruited 26 KTRs treated with tacrolimus (TAC) -based regimen, 13 with sirolimus (SRL) -based regimen and 10 healthy controls (HC) in this study. The percentage and absolute number of circulating Tfh cells and the co-expression of Tfh related molecules including inducible costimulatory molecule (ICOS), programmed cell death protein 1 (PD-1), interleukin-21 (IL-21) and signal transducer and activator of transcription 3 (STAT3) were analyzed by flow cytometry, while serum IL-6 was detected by electrochemiluminescence immunoassay. ResultsThe percentage and absolute number of Tfh cells and the co-expression of PD-1, STAT3 in Tfh cells were significantly higher in TAC group than that in SRL group. While no difference was found in regard to IL-21 and ICOS co-expressed with Tfh cells among three groups. Multiple linear regression analysis results showed that pre-transplant PRA level was the significant confounder affecting the absolute numbers of Tfh and CD4+CXCR5+PD-1+ T cells. In addition, correlation analysis showed that CD4+CXCR5+STAT3+ T cells were positively correlated to Tfh cells. ConclusionsOur study indicates that sirolimus can suppress the quantity of Tfh cells more significantly than tacrolimus. The higher level of circulating Tfh cells in tacrolimus group might be related to STAT3 signaling.

Immunosuppressive Treatment Alters Secretion of Ileal Antimicrobial Peptides and Gut Microbiota, and Favors Subsequent Colonization by Uropathogenic Escherichia coli

Transplant recipients are treated with immunosuppressive (IS) therapies, which impact host-microbial interactions. We examined the impact of IS drugs on gut microbiota and on the expression of ileal antimicrobial peptides. Mice were treated for 14 days with prednisolone, mycophenolate mofetil, tacrolimus, a combination of these 3 drugs, everolimus, or water. Feces were collected before and after treatment initiation. Ileal samples were collected after sacrifice. Fecal and ileal microbiota were analyzed by pyrosequencing of 16S rRNA genes and enumeration of selected bacteria by culture, and C-type lectins were assessed in ileal tissues by reverse transcriptase-quantitative polymerase chain reaction. Prednisolone disrupted fecal microbiota community structure, decreased Bacteroidetes, and increased Firmicutes in the feces. Prednisolone, tacrolimus, and mycophenolate mofetil modified fecal microbiota at the family level in each experimental replicate, but changes were not consistent between the replicates. In ileal samples, the genus Clostridium sensu stricto was dramatically reduced in the prednisolone and combined IS drug groups. These modifications corresponded to an altered ileal expression of C-type lectins Reg3γ and Reg3β, and of interleukin 22. Interestingly, the combined IS treatment enabled a commensal Escherichia coli to flourish, and dramatically increased colonization by uropathogenic E. coli strain 536. IS treatment alters innate antimicrobial defenses and disrupts the gut microbiota, which leads to overgrowth of indigenous E. coli and facilitates colonization by opportunistic pathogens.

Impact of immunosuppressive drugs on the therapeutic efficacy of ex vivo expanded human regulatory T cells.

Immunosuppressive drugs in clinical transplantation are necessary to inhibit the immune response to donor antigens. Although they are effective in controlling acute rejection, they do not prevent long-term transplant loss from chronic rejection. In addition, immunosuppressive drugs have adverse side effects, including increased rate of infections and malignancies. Adoptive cell therapy with human Tregs represents a promising strategy for the induction of transplantation tolerance. Phase I/II clinical trials in transplanted patients are already underway, involving the infusion of Tregs alongside concurrent immunosuppressive drugs. However, it remains to be determined whether the presence of immunosuppressive drugs negatively impacts Treg function and stability. We tested in vitro and in vivo the effects of tacrolimus, mycophenolate and methylprednisolone (major ISDs used in transplantation) on ex vivo expanded, rapamycin-treated human Tregs. The in vitro results showed that these drugs had no effect on phenotype, function and stability of Tregs, although tacrolimus affected the expression of chemokine receptors and IL-10 production. However, viability and proliferative capacity were reduced in a dose-dependent manner by all the three drugs. The in vivo experiments using a humanized mouse model confirmed the in vitro results. However, treatment of mice with only rapamycin maintained the viability, function and proliferative ability of adoptively transferred Tregs. Taken together, our results suggest that the key functions of ex vivo expanded Tregs are not affected by a concurrent immunosuppressive therapy. However, the choice of the drug combination and their timing and dosing should be considered as an essential component to induce and maintain tolerance by Treg.

Role of vaccinations and prophylaxis in rheumatic diseases.

Targeted strategies for reducing the increased risk of infection in patients with autoimmune rheumatic diseases include vaccinations as well as antibiotic prophylaxis in selected patients. However, there are still issues under debate: Is vaccination in patients with rheumatic diseases immunogenic? Is it safe? What is the impact of immunosuppressive drugs on vaccine immunogenicity and safety? Does vaccination cause disease flares? In which cases is prophylaxis against Pneumocystis jirovecii required? This review addresses these important questions to which clinicians and researchers still do not have definite answers. The first part includes immunization recommendations and reviews current data on vaccine efficacy and safety in patients with rheumatic diseases. The second part discusses prophylaxis for Pneumocystis pneumonia.

The kinetics of urinary shedding of BK virus in children with renal disease.

Children with renal diseases are typically treated with immunosuppressive drugs, which place them at high risk of reactivation of the BK virus (BKV). Currently, little is known about the impact of immunosuppressive drugs on the kinetics of urinary shedding of BKV and viral reactivation in pediatric patients with renal diseases. Urine samples were collected monthly for 1 year from 20 children (median age, 9 years; range, 4-15 years) with renal diseases and subjected to real-time PCR. Urinary shedding of BKV was detected in 35% (7/20) of the patients, three of these patients having persistent viral DNA excretion (two cases, twelve times; one case, four times) and four having intermittent viral DNA excretion. Thirty-four of the 240 urine samples contained BKV DNA (median copy numbers, 5.66 log copies/mL; range, 2.45-7.69 log copies/mL). In two of the cases with persistent viral shedding, high copy numbers (range, 4.57-7.69 log copies/mL) of BKV DNA were detected in all 12 urine samples collected. In the other case with persistent viral excretion, a range of 2.45-3.98 log copies/mL of BKV DNA was detected in the four urine samples collected between the 9th and 12th sampling time points. Additionally, high copy numbers (range, 3.12-4.36 log copies/mL) of BKV DNA were detected intermittently in the urine samples of the other four cases. No remarkable correlations were found between the kinetics of BKV DNA loads and urinary findings such as proteinuria and hematuria. The present data demonstrate the kinetics of urinary BKV shedding in pediatric patients with renal diseases. Additionally, no pathogenic role for BKV infection was identified.

Clinically-relevant cyclosporin and rapamycin concentrations enhance regulatory T cell function to a similar extent but with different mechanisms: an in-vitro study in healthy humans.

Evidence indicates that regulatory T cells (Tregs) are profoundly involved in promoting allograft tolerance after organ transplantation. Since a successful transplantation currently still requires a long-term immunosuppressive treatment, clarifying the specific impact of these drugs on Tregs may be of high clinical relevance. Conflicting results arise from the literature, particularly as concerns cyclosporine (CsA). The specific aim of this work was to evaluate in-vitro the direct effects of clinically-relevant drug concentrations of three widely used immunosuppressive drugs, i.e. CsA, rapamycin (RAPA) and mycophenolic acid (MPA), on Treg activity, number and forkhead/winged helix transcription factor (FoxP3) expression in humans. Tregs (CD4(+)CD25(+)) isolated from healthy donors were cultured in the presence of different concentrations of CsA, RAPA or MPA. The suppressive activity of Tregs was evaluated in mixed lymphocyte reactions with CD4(+)CD25(-) T cells. Phenotype analysis and FoxP3 expression were assessed by flow cytometry. Clinically-relevant CsA and RAPA concentrations significantly enhanced to a similar extent the suppressive activity of Tregs. Although this effect was associated with an increase in Treg number as well as in FoxP3 expression with both drugs, the driving mechanism seemed to be primarily quantitative (i.e. increase of the cell number) for RAPA, whereas mainly qualitative (i.e. increase in FoxP3 levels) for CsA, respectively. Conversely, MPA did not show any effect on Treg function and number. These findings suggest that both RAPA and CsA may be beneficial in promoting Treg-dependent allograft tolerance after organ transplantation.

P143 Screening for latent tuberculosis in patients with inflammatory bowel diseases: impact of immunosuppressive drugs in the performance of an interferon-gamma release assay

P143 Screening for latent tuberculosis in patients with inflammatory bowel diseases: impact of immunosuppressive drugs in the performance of an interferon-gamma release assay

Impact of Mycophenolic Acid and Tacrolimus on Th17-Related Immune Response

Little is known on the impact of immunosuppressive drugs on the development of the different T-cell subsets that compose the immune balance. We have explored the influence of mycophenolic acid (MPA) and tacrolimus on T cells response with a special focus on the Th17-cell subset. In an in vitro model of human CD4 cells activation, we first compared the influence of MPA and tacrolimus on the transcription of different set of genes related to each of the main T-cell subsets and then investigated how these two drugs interfere with interleukin (IL)-17 production. We also studied, in stable kidney transplant patients, the relation between IL-17 serum concentration and systemic drug exposure. MPA and tacrolimus exhibited a comparable impact on T-cell response, dampening most Th1-related genes transcription and preserving regulatory T cells/Th2 molecular phenotypes. Although both MPA and tacrolimus decreased Th17-related transcripts after T-cell activation, MPA exerted a stronger inhibitory effect on IL-17 production than tacrolimus. Accordingly, renal transplant patients treated with MPA in combination with minimized dose of tacrolimus tended to have lower circulating IL-17 levels than patients treated with tacrolimus alone given at conventional dose. A treatment combining MPA and tacrolimus is susceptible to favorably tip the immune balance and might confer optimal allograft immunoprotection. Because of its ability to profoundly inhibit IL-17 production, MPA may help to better overcome Th17-related alloreactivity in the context of calcineurin inhibitor-minimizing protocol.

Impact of Immunosuppressive Drugs on the Development of Cardiac Allograft Vasculopathy

Immunosuppressive drugs (ISDs) have a major impact on the development and progression of cardiac allograft vasculopathy (CAV), the main cause of cardiac allograft loss and a leading cause of death beyond the 1st post-transplant year. The influence of ISDs on the development and progression of CAV is complex. In spite of their high potency to suppress the alloimmune response (prevention of allograft rejection) which plays an essential role in the pathogenesis of CAV, the immunosuppressive regimens which were used in the past were not able to entirely prevent the development of CAV. This can be explained by the fact that several non-alloimmune insults such as brain death, organ preservation, surgical trauma, ischemia-reperfusion, diabetes, hypertension, hyperlipidemia, cytomegalovirus infection etc. are also involved in the development or progression of CAV. Some of these insults are not affected by immunosuppression, whereas others can be even aggravated by certain ISDs, particularly by calcineurin inhibitors (CNIs), but also by glucocorticosteroids and proliferation signal inhibitors (PSIs). Certain ISDs, especially CNIs, also have direct toxic effects on vascular endothelial and smooth muscle cells inducing endothelial dysfunction and proliferation of both smooth muscle cells and fibroblasts which promotes the development and progression of CAV. Other ISDs like PSIs and mycophenolate mofetil appeared able to delay the onset of CAV and reduce its progression, especially by their inhibitory effects on smooth muscle cell migration and proliferation. The present article reviews the data available on the impact of different ISDs and regimens on the development and progression of CAV.

Organ transplantation and skin cancer: basic problems and new perspectives

Solid organ transplant and subsequent graft survival have increased worldwide, while immunosuppression has prevented rejection with increasing success. Side effects of cutaneous infection and neoplasm, however, affect the majority of solid organ transplant recipients (OTRs). Squamous cell carcinoma of the skin (SCC) is the most common neoplasm overall following organ transplant with a risk that is 60-100 times greater than for the immunocompetent population. This review focuses on questions of ongoing debate about SCC formation in OTRs such as viral carcinogenesis, systemic photoprotection, photosensitization by drugs, the impact of immunosuppressive drugs and inflammation as a driver of carcinogenesis.

Calcineurin inhibitors affect B cell antibody responses indirectly by interfering with T cell help

In general, humoral immune responses depend critically upon T cell help. In transplantation, prevention or treatment of humoral rejection therefore require drugs that ideally inhibit both B cell and T helper cell activity. Here, we studied the effects of commonly used immunosuppressive drugs [tacrolimus, cyclosporin, mycophenolic acid (MPA) and rapamycin] on T cell helper activity and on T cell-dependent B cell responses. T cells were activated polyclonally in the presence of immunosuppressive drugs in order to analyse the effect of these drugs on T cell proliferation, co-stimulatory ligand expression and cytokines. The impact of immunosuppressive drugs on T cell-dependent immunoglobulin production by B cells was addressed in T-B cell co-cultures. All drugs affected T cell proliferation and attenuated T cell co-stimulatory ligand (CD154 and CD278) expression when T cells were activated polyclonally. Tacrolimus, cyclosporin and rapamycin also attenuated B cell stimulatory cytokine mRNA levels in T cells. As a consequence, a decrease in immunoglobulin levels was observed in autologous T-B cell co-cultures, where T cell help is essential for immunoglobulin production. In contrast, when pre-activated T cells were used to stimulate autologous B cells, calcineurin inhibitors failed to inhibit B cell immunoglobulin production, whereas MPA and rapamycin did show inhibition. From these studies, it is evident that calcineurin inhibitors affect the humoral immune response by interfering with T helper signals, but not by targeting B cells directly. Furthermore, our studies support the necessity of intervening in T cell helper function to attenuate humoral responses.