Question

Helllpppppp on this two immunology question pleaseee?

1. Describe how Treg negatively regulate immune responses?

2. Describe how innate immunity collaborates with adaptive immunity to protect the host by using DC (dendritic cells) as an example?

Answer 1

Answer 1:

Regulatory T cells (Tregs) are a heterogeneous subset of CD4+ T cells with immunosuppressive properties that are required to maintain immune homeostasis and self-tolerance, dampen inflammation, and prevent autoimmunity. Tregs function by inhibiting the activities of CD4+ and CD8+ effector T cells (Teff cells), natural killer (NK) cells, NKT cells, and antigen-presenting cells through multiple mechanisms. These include the secretion of inhibitory cytokines, disruption of effector T cell metabolism, production of cytolytic factors, induction of infectious tolerance, and modulation of dendritic cell maturation or function.

One mechanism by which Tregs suppress T cell-mediated immune responses is through the secretion of immunosuppressive cytokines such as TGF-β, IL-10, and IL-35. Each of these cytokines is involved in inhibiting the differentiation, proliferation, and activation of Teff cells, suppressing cytokine production by Teff cells, and promoting the conversion of activated T conventional (Tconv) cells to cells with an immunosuppressive phenotype.

Another mechanism by which Tregs suppress effector T cell functions is through metabolic disruption. High level expression of IL-2 Rα/CD25 on the surface of Tregs has been suggested to deplete local IL-2, leading to deprivation-mediated Teff cell apoptosis. Tregs also inhibit Teff cell proliferation and IL-2 synthesis by directly transferring inhibitory cAMP through the gap junctions of Teff cells.

Answer 2:

Dendritic cells (DCs) represent a heterogeneous family of immune cells that link innate and adaptive immunity. The main function of these innate cells is to capture, process, and present antigens to adaptive immune cells and mediate their polarization into effector cells. DCs can be subdivided in two main subtypes: plasmacytoid (pDC) and myeloid (mDC) DCs, which specialize in the recognition of different pathogen associated molecular patterns (PAMPs) due to the unique distribution of Pattern Recognition Receptors (PRR), such as toll-like receptors, C-type lectins and intracellular nucleic acid sensors. As a result, mDCs and pDCs can efficiently induce CD4+ and CD8+ T cell responses against different types of pathogens. In addition, both mDCs and pDCs are also capable of interacting with Natural Killer (NK) cells, which are particularly relevant during viral infections. Therefore, the contribution of different DC subtypes to immune responses against microbial infections seems to be highly complex and be influenced by context- and pathogen-dependent factors.