Dendritic cells in contact sensitivity

Tbet and IL-36γ cooperate in therapeutic DC-mediated promotion of ectopic lymphoid organogenesis in the tumor microenvironment

We have previously reported that direct injection of dendritic cells (DC) engineered to express the Type-1 transactivator Tbet (i.e., DC.Tbet) into murine tumors results in antitumor efficacy in association with the development of structures resembling tertiary lymphoid organs (TLO) in the tumor microenvironment (TME). These TLO contained robust infiltrates of B cells, DC, NK cells, and T cells in proximity to PNAd⁺ blood vessels; however, they were considered incomplete, since the recruited B cells failed to organize into classic germinal center-like structures. We now report that antitumor efficacy and TLO-inducing capacity of DC.Tbet-based i.t. therapy is operational in peripheral lymph node-deficient LTA^-/- mice, and that it is highly dependent upon a direct Tbet target gene product, IL-36γ/IL-1F9. Intratumoral DC.Tbet fails to provide protection to tumor-bearing IL-36R^-/- hosts, or to tumor-bearing wild-type recipient mice co-administered rmIL-1F5/IL-36RN, a natural IL-36R antagonist. Remarkably, the injection of tumors with DC engineered to secrete a bioactive form of mIL-36γ (DC.IL36γ) also initiated therapeutic TLO and slowed tumor progression in vivo. Furthermore, DC.IL36γ cells strongly upregulated their expression of Tbet, suggesting that Tbet and IL-36γ cooperate to reinforce each other's expression in DC, rendering them competent to promote TLO formation in an "immunologically normalized," therapeutic TME.

The role of dendritic cells in immune responses against vaginal infection by herpes simplex virus type 2

Herpes simplex virus type 2 is a leading cause of genital ulcers that affects more women than men worldwide. Recent evidence indicates that protective immunity can be generated by specialized dendritic cells in the female genital mucosa. This article aims to provide an overview of the effector immunity required for protection from genital herpes, and to discuss the mechanism by which specific subsets of dendritic cells mediate induction of adaptive immunity following genital infection with herpes simplex virus type 2 in vivo.

Effect of coadministration of corticosteroids on the development of contact sensitization

BACKGROUND

Transdermal administration of drugs can increase patient compliance and reduce side effects, but it can also cause contact sensitization. Corticosteroids frequently are used to suppress the local immune response; however, their use as a pretreatment for transdermal system application sites is not practical.

OBJECTIVE

Our purpose was to determine the feasibility of suppressing contact sensitization by delivering a corticosteroid with the transdermal delivery systems.

METHODS

Materials were applied continuously for 3 weeks to the same (protocol SS) or different (protocol AS) skin sites. Skin flux and appearance of sensitization were determined.

RESULTS

Coadministration of hydrocortisone reduced the incidence of sensitization by d-chlorpheniramine and benzoyl peroxide from 45% to 7.5% and from 20% to 2.3%, respectively, under protocol SS. Under protocol AS, sensitization by d-chlorpheniramine was reduced from 15% to 1%. Frequent exposure to the sensitizer plus corticosteroid induced tolerance to the sensitizer.

CONCLUSION

Sensitization by moderately immunogenic drugs after any length of exposure may be reduced to acceptable levels by the coadministration of hydrocortisone.

Pilot study of topical dinitrochlorobenzene (DNCB) in human immunodeficiency virus infection

Dendritic cells, the primary antigen presenting cells of the human immune system, are heavily infected with human immunodeficiency virus (HIV) in patients with the acquired immunodeficiency syndrome (AIDS). Dinitrochlorobenzene (DNCB) is a contact sensitizing agent that acts as a potent immune modulator of dendritic cells. In this pilot study, we examined the safety and efficacy of topical DNCB application in patients with early HIV disease. Topical DNCB was well tolerated by these patients, with an adverse reaction rate of 10%. CD4+ T-cell counts remained stable with repeated DNCB use. In contrast, CD8+ T-cell counts and natural killer cells increased significantly following DNCB sensitization. This increase in CD8+ T-cell and natural killer cell subsets was accompanied by a decrease in HIV replication, as measured by serum HIV RNA levels. Based on this pilot study, we conclude that topical DNCB is safe in early HIV disease and may decrease viral load via a systemic effect on dendritic cells, CD8+ T-cells and natural killer cells. These results require confirmation in larger controlled trials.

Development and function of dendritic cells in health and disease

The life history of dendritic cells (DC) is now established from their origins from bone marrow stem cells, their distribution through blood to the tissues, and their movement via afferent lymph to lymph nodes for the initiation of immune responses. Bone-marrow stem cells, and occasional stem cells in peripheral blood (about 1 per 10(5) mononuclear cells), can give rise both to DC and macrophages (MO). In addition to stem cells in blood, after short-term culture of mononuclear cells, three major morphologic types of DC can be separated (types I-III), which probably represent the maturational pathway of this cell type; type II cells resemble tissue DC such as Langerhans cells and type III have a veiled morphology similar to that seen in cells of afferent lymph and in the interdigitating cells of the paracortex of lymph nodes. Functionally, DC cultured from peripheral blood are able to acquire large antigens and process them like Langerhans cells of the skin. They can also present antigens to stimulate primary T-cell responses, a property associated with lymph node DC. In tissues, DC appear to act as outposts of the immune system, acquire antigens, and, particularly in primary responses, carry the antigens to lymph nodes where they initiate T-cell responses. In secondary responses, activation of memory T cells in the periphery and the acquisition of antigen/antibody complexes by follicular dendritic cells of the lymph node follicles, which stimulate B cell memory, may be more important pathways for immune activation. DC may play a role in the development of many immunologic diseases including cancer, autoimmunity, and acquired immunodeficiency syndrome (AIDS).

Dendritic cells and dinitrochlorobenzene (DNCB): a new treatment approach to AIDS

Recent studies suggest that antigen-presenting cells (dendritic cells) may play a key role in the pathogenesis of human immunodeficiency virus (HIV) infection. This observation makes new immunomodulatory treatment strategies desirable. Topical dinitrochlorobenzene (DNCB) is discussed as a possible treatment modality in the context of its proven therapeutic uses and its immunomodulatory effect on dendritic cells. DNCB may be a safe, inexpensive, and widely available treatment option for HIV disease.

Interstitial dendritic cells

Interstitial dendritic cells (IDC) were first identified in the interstitium of non-lymphoid organs as leucocytes which stained intensely with anti-MHC class II antibodies. These cells have been identified in several species including man, and can be distinguished from tissue macrophages by their immunological phenotype and cytochemical and functional characteristics. IDC appear to be closely related to lymphoid dendritic cells (DC), and have the capacity to bind antigen and stimulate T lymphocyte responses. It seems probable that they represent a stage of nonlymphoid dendritic cell differentiation necessary for antigen surveillance, similar to the Langerhans cell of the skin. Exposure to antigen appears to induce migration of these cells into adjacent lymphatics and subsequent localization in the interfollicular areas of lymph node, where the DC present processed antigen to activate a primary T cell response. The IDC has been identified as the passenger leucocyte within organ allografts which contributes substantially to graft immunogenicity, so that eradication of donor organ IDC improves organ graft survival.