Use the default signature from outlook

Does anyone know how to add the signature from outlook to this code?  I have a default signature that I use for outlook.  In addition, my recipients for this code is a group contact, so I want to make sure that the code that I have is not a problem.  

Imports Excel = Microsoft.Office.Interop.Excel
Imports Olook = Microsoft.Office.Interop.Outlook

Public Class Form1
    Dim xlApp As New Excel.Application
    Dim xlWorkBook As Excel.Workbook
    Dim xlWorkSheet As Excel.Worksheet
    Dim xlRange As Excel.Range
    
    Private Sub btnSendEmail_Click(sender As Object, e As EventArgs) Handles btnSendBeginningEmail.Click
        Dim Outlook As New Microsoft.Office.Interop.Outlook.Application
        Dim MailItem As Microsoft.Office.Interop.Outlook.MailItem
        Dim signature As String
        MailItem = Outlook.CreateItem(Microsoft.Office.Interop.Outlook.OlItemType.olMailItem)
        signature = MailItem.Body
        With MailItem
            .Body = signature
            .Subject = "Beginning ISIR Downloads"
            .Recipients.Add("ISIR Downloads")
            .Display() 'opens the email for checking prior to sending or use .Send()
        End With
    End Sub
End Class

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