### Overview of the CD86 Gene

**Gene Symbol**: CD86  
**Location**: Chromosome 30 (30q13.2) in humans  
**Protein**: CD86 is a type I membrane protein that plays a crucial role in T-cell activation and regulation of immune responses.  

**Function**: CD86 is primarily expressed on antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells. It serves as a ligand for the T-cell surface proteins CD28 and CTLA-4 (cytotoxic T-lymphocyte-associated protein 4). The binding interactions mediate critical immunological responses:
- Binding to CD28 provides a costimulatory signal necessary for T-cell activation and proliferation.
- Binding to CTLA-4 inhibits T-cell activation, thus acting as a checkpoint that downregulates immune responses.

### 1. Associated Genes
Though the provided summaries highlight interactions with CD28 and CTLA-4, other genes that are associated with CD86 include:
- **CD80**: Another costimulatory molecule that also interacts with CD28 and CTLA-4. 
- **PD-L1 (CD274)**: Involved in immune checkpoint regulation.
- **ICOS (Inducible T-cell COStimulator)**: Plays a role in T-cell activation and survival.
- **TNF (Tumor Necrosis Factor)**: Involved in inflammatory responses.
  
There may also be indirect associations with genes related to broader immune signaling pathways and cytokines, including IL-2 and IL-6.

### 2. Aging and Age-Related Diseases
Research has indicated that CD86 expression levels can change with age, potentially leading to altered immune responses:
- **Immunosenescence**: Increased expression of costimulatory molecules, including CD86, has been noted in elderly individuals, which may contribute to age-related decline in immune function.
- **Autoimmune Diseases**: Dysregulation of CD86 and its interactions may be associated with increased susceptibility to autoimmune diseases, which often exhibit higher prevalence in older populations.
- Some studies suggest that altered CD86 expression may influence chronic inflammation, which is commonly observed in age-related diseases such as arthritis and cardiovascular diseases.

### 3. Drug Interactions
Due to its role as a costimulatory molecule, CD86 is implicated in various therapeutic areas in immunology:
- **Monoclonal Antibodies**: Drugs targeting CD86, such as abatacept (Orencia), are used to treat autoimmune diseases like rheumatoid arthritis. Abatacept works by inhibiting the interaction between CD80/CD86 on APCs and CD28 on T cells.
- **Immunotherapeutics**: CTLA-4 blockers (like ipilimumab) affect the CD86-CD28 interaction indirectly by blocking the inhibitory pathway.

### 4. Pathways and Biological Processes
CD86 is involved in multiple biological pathways and processes:
- **T-cell Activation**: Critical role in the initial activation of naïve T-cells.
- **Costimulation**: Works in conjunction with other molecules like CD80 to enhance T-cell responses.
- **Immune Response**: Plays an important role in both the priming and regulation of immune responses, balancing activation and anergy.
- **Signal Transduction**: Involvement in the NF-kappa-B signaling pathway upon CD40 engagement, which is vital for adaptive immunity.

**Biological Processes**:
- **Positive Regulation of T-cell Proliferation**: Facilitating T-cell growth and survival.
- **B-cell Activation**: Influencing antibody production, particularly IgG.
- **Cytokine Production**: Modulating the secretion of various cytokines, influencing inflammation and immune responses.

In summary, the CD86 gene is pivotal for immune regulation, impacting T-cell functionality and has significant implications for aging and therapeutic strategies in immunotherapy.