By Stacy Jenel Smith April is Autism Awareness Month - an especially meaningful matter to a number of Hollywood's best-known names, whose children are affected by the neuro-developmental disorder that causes communication difficulties and problems with social interactions. It's a disorder that, clearly, hits families anonymous and famous, of modest means and enormous wealth alike.

For stars the likes of Joe Mantegna, Gary Cole and Aidan Quinn, autism is a fact of daily life. Like parents of autistic children everywhere, their responses to that fact are varied, and passionate.

"In 20 years we will be shaking our heads and be aghast at what we allowed to happen," declares Quinn. The actor is involved in several autism-related organizations, and is among those who adamantly believe over-use of immunizations is the primary factor in the surge of autism in all its varying degrees. "The incidence of autism has gone up 500 per cent since my daughter was diagnosed," he says. (Current estimates have a child being diagnosed with autism every 21 minutes.)

A story Aidan would really like to do on film would be one that showed over-immunization, pushed by drug companies, causing autism and other disorders.

"I'm sure that was the cause in my daughter's case. She went into convulsions after being immunized," he says. "I know the pain and the grief and the difficulty, and not just to my own immediate family but to my extended family - so every time I see a person I know even glancingly who is pregnant, I say, 'Please, look into the immunization thing and make your own choices.'"

Edward Asner has also been among the actors at the forefront of autism fundraising and awareness-raising. As the parent of an 18-year-old autistic son, the esteemed actor has been witness to dramatic changes in diagnosis and treatment of the condition - as well as what he terms its "mushrooming" numbers.

In the case of son Charlie, it took years before his autism was diagnosed "by the experts at UCLA. This was after the psychologist, the speech therapist, the neurologist and many teachers - none of whom could adequately blow the whistle on this thing," says the former Screen Actors Guild President, who remains politically involved. "I felt a great deal of anger, not at him, but at the situation. The fact is, we're still in the shadows here. Supposedly the experts can tell you what the difference is between high functioning autism and Asperger's syndrome. I can tell you one big difference: there's government aid for one and not the other."

Joe Mantegna, who has been making autism public service spots and appearing at autism-related events for years, and his wife Arlene have two daughters. The elder, Mia, 18, is autistic, yet highly functioning.

"I'm a firm believer, you play the cards you're dealt in life," says Joe. "I wish she didn't have to deal with it, but she's a happy girl. She knows she's autistic but it doesn't seem to impact her in a negative way as much as it does the support group around her. We try to keep her as involved in the world as possible, and it's okay. People are kind and understanding if you meet them half-way," he says, "and her sister (Gina) is a remarkable human being.

"I really believe there is a plan out there," he adds, noting that he was on "Joan of Arcadia," a "show where my daughter talked to God. It's almost easier to believe in something than not, when you look at all the beauty and wonder in the world. It's hard to imagine it all being some magical accident. In spite of the spurts of tragedy and ugliness, you have to think that if there is some sort of logic to it, we're evolving toward the light. If this is part of the plan, I accept my role gladly and graciously. I am such a blessed person in so many aspects of my life."

Mantegna, who has visited Mia's classes - she has been in mainstream school rooms - and given talks about autism, is also positive about acceptance he's found: "I think when you talk to the kids and explain autism to them they rise to the occasion. God bless those kids who are best friends to an autistic child."

Gary Cole is grateful for the help provided his 12-year-old daughter, Mary, by Tattinger, her furry best friend. As recounted in the book "Love Heels: Tales from Canine Companions for Independence," Cole and wife Teddi had their autistic little girl in to see a myriad of specialists and undergo various therapies before being astonished at her interest in a friend's dog at a Christmas party. Teddi contacted Canine Companions for Independence, and eventually Mary wound up with the pooch who caused an immediate change in her. She was calmer, more focused, more communicative. The Coles would love to see more autistic kids teamed with canine pals -- the ultimate loving and non-judgmental sidekicks.

Behind the scenes, many more of the entertainment industry's key players are involved in the fight against autism -- including film producer Jonathan Shestack, who along with his wife Portia Iversen founded Cure Autism Now (CAN). Shestack's son has autism. And NBC Universal CEO Bob Wright and his wife Suzanne, whose grandson has autism, founded the organization Autism Speaks to help fight the disorder.

Many more celebrities are involved in helping - some of whom have autistic family members, some of whom don't. In the case of long-time CAN supporter and 8-year board member Anthony Edwards, he was looking for a children-related cause to put his energies into when "ER" gave him a big jolt of fame to work with. He has a cousin whose child is autistic. Among other activities on behalf of CAN, Edwards successfully lobbied Congress for passage of the Children's Health Act of 2000 - but notes that there's still work ahead, seeing to it that the legislation is actually enacted.

Turning out for CAN's Los Angeles Walk Now fundraiser April 22 are names including "CSI: Miami's" Eva La Rue, "The West Wing's" Richard Schiff, "The Shield's" David Marciano and Cathy Cahlin Ryan and her husband, the show's creator, Shawn Ryan, and teacher/producer/leader of Actors Against Autism Joey Travolta - as well as this writer. Walk Now events will be taking place in cities all over the country throughout the spring and summer. For information, check out www.walknow.org.