Have you got a reference for glTexImage2D anywhere? It’s probably outdated since your third parameter shouldn’t be an integer value anymore. From memory older MSDN uses integers in its help system description of the function so you should update your MSDN documentation.
The third parameter is the internal format of the texture i.e. how OpenGL stores the texture internally. Integer values for internal format are kept to ensure compatibility with OpenGL 1.0. What you should have for a luminance-alpha texture is GL_LUMINANCE_ALPHA. You can also specify the bits used for each e.g. GL_LUMINANCE8_ALPHA8.
So, in your case, your call should look like this: