When actor Sidney Poitier described Leah Tutu and her husband, Bishop Desmond Tutu, as "a light in the moral darkness of South Africa," Mrs. Tutu didn't smile.

And she didn't stir or smile when the table chatter at the TransAfrica annual dinner Saturday paused for a taped message from her husband, secretary-general of the South African Council of Churches, who remains in South Africa. His passport was withdrawn recently because of his outspokenness against the white majority-dominated South African government.

"I am delighted that modern technology has enabled us to frustrate the efforts of those opposed to us," Tutu's taped voice said with solomn precision. "I am puzzled why they fear little me when I do not even have the vote in my country and when they describe me as a self-appointed leader who has no constituency or following. It is strange that the should spend so much of their energies and attention on nullifying a nonentity such as me."

As the audience of 1,300 at the fund-raiser for the African and Caribbean lobbying group appreciatively laughed and cheered, the bishop spoke of solidarity with the American human rights movement, of the inspiration he received from American figures such as Joe Louis, Louis Armstrong and Jackie Robinson, and then issued a warning, urging pressure on the government of South Africa for negotiations on the country's future "before it is too late."

There on a stage at the Washington Hilton, with historian Rayford Logan, another of the evening's honorees, Leah Tutu was a quiet messenger, a figure of comfort and compassion. But earlier that day, when the spotlight was on her own words and actions, she was an exuberant teacher.

Sitting in an art-filled living room where 25 women and four men had gathered to hear her views on political movements in southern Africa, Leah Tutu, 47, was asked by a young South African woman if she should feel guilty for living in the United States. "Help me to dispel that, if you can," the woman said. "I would love to make you feel guiltier," was the soft reply.

Tutu, director of the Domestic Workers' Employement Project in her country, described the problems of millions of women, aged 16 to 60, who have had little schooling and earn approximately $90 a month, who have no family life, who live in cell-like conditions. "They live in a room the size of a small bathroom. They can't entertain and can be arrested if someone visits them after 10 p.m.," she said.

But she offered very careful and moderate criticism of other policies, such as the creation of Bantustans, or black areas that are called countries by the South Africa government but are not recognized by other nations. "What they are is a holiday resort for white South Africans. They have Holiday Inns, and have all the books banned in South Africa and they can have [interracial relations], which is forbidden. No black South Africans in their proper mind would recognize it as a country," said Tutu.

She used her humor to dispel her anxiety at the controls over black mobility and expression at home. "This time I think I ought to write a thank-you letter to the prime minister for a change," she said, referring to events that enabled her to substitute for her husband at the TransAfrica dinner.

Tutu, the daughter of a domestic who was widowed when she was pregnant with her third child, learned firsthand of the misery of that work. Routine incidents taught her the larger lessons of apartheid in her husband. "My older brother worked in a factory, and one of the managers there asked him to do some gardening on the weekends. The man gave him a rug, which he kept in his room. The police came one night on a raid, went into my brother's room and said it couldn't be possible for him to own the rug. And they arrested him for stealing," recalls Tutu.

Tutu, who wanted to be a nurse, got a teaching degree and taught in her township. Then she met the family of Desmond Tutu. Her candor about the bishop seems to spring from a personal confidence, unaffected by the physical distance between them. "To me then, he was somebody who was stuck-up," she says. Later, in describing her reaction when he switched from a teaching career to the ministry, she says, "That was shattering news . . . I thought ministers were special people."

Her husband's ministry gave Leah Tutu a Christian approach to venting her hatred of apartheid, as well as enabling her to escape nonpersonhood in her own country through eight years of residence in London.

It was a tremendous growing experience for her, not only because of her acceptance as an equal and her expanding political views but also through the freedom of self-expression.

"I went to the Adult Education Centers and took car maintenance -- mainly because Desmond was traveling a lot, so I thought a knowledge of that would help -- yoga for vanity, and psychology because it stretched my mind," she said. When, in 1975, her husband was ready to go home, she was upset. "We were buying a house and I didn't want to break up the family," she says. "My argument was, I did want us to go home at some point, but his arguments was that was as good a time as any."

Back in South Africa, with her children in boarding school in Swaziland, she opted for involvement with the domestic workers' movement, rather than pouring tea for the bishop's parishioners. Although she knows her work isn't as far-reaching as her husband's and her symbolismn of struggle isn't as dramatic as that of a woman she admires, Winnie Mandela, the banned and exiled wife of imprisoned black leader Nelson Mandela, She nonetheless says she is fulfilled.She has the rare privilege of being able to see South Africa both from outside -- she was with her husband earlier this year when he met Pope John Paul II and the archbishop of Canterbury -- and inside. But she isn't exluded from harassment. When she was on her way to the funeral of Steve Biko, the black leader who died in policy custody nearly three years ago, the bus she was on was stopped, searched and seized.She never got to the funeral.

Her view of any government backlash against her remarks is one of iron resignation. "I am not afraid. I do expect repercussions," she says, a thin smile showing her retreat into private thoughts. "I don't go out to get repercussions, but I am not afraid of whatever stand they can take."