At the top of this panel we see the Alpha and Omega. The first and last letters of the Greek alphabet represent Jesus Christ.

I am the Alpha and the Omega, the first and the last, the beginning and the end.

Revelation 22:13

The vine surrounding the Alpha and Omega also symbolizes Christ.

I am the true vine, and my Father is the vine grower.

John 15:1

In the main panel we see Christ as the Good Shepherd tending his flock and holding a lamb while the lamb is also frequently a symbol for Christ.

Worthy is the Lamb who was slain, to receive power and wealth and wisdom and might and honor and glory and blessing!" And I heard every creature in heaven and on earth and under the earth and in the sea, and all therein, saying, "To him who sits upon the throne and to the Lamb be blessing and honor and glory and might for ever and ever!" And the four living creatures said, "Amen!" and the elders fell down and worshiped.

Rev 5:12-14